Single domain antibody and derivative proteins thereof against programmed death-ligand (pdl1)

ABSTRACT

The present invention relates to the field of medical biology, and discloses a single domain antibody and derivative proteins thereof against programmed death ligand (PDL1). In particular, the present invention discloses a programmed death ligand 1 (PDL1) binding molecular and the use thereof, especially the use for treating and/or preventing or diagnosing PDL1 relevant diseases such as tumor.

TECHNICAL FIELD

The present invention relates to the field of medical biology, anddiscloses a single domain antibody and derivative proteins thereofagainst programmed death ligand (PDL1). In particular, the presentinvention discloses a programmed death ligand 1 (PDL1) binding moleculeand the use thereof, especially the use for treating and/or preventingor diagnosing PDL1 relating diseases such as tumor.

BACKGROUND

Programmed death 1 (PD-1) is a member of the CD28 family of receptors,which includes CD28, CTLA-4, ICOS, PD-1, and BTLA. The initial membersof the family, CD28 and ICOS, were discovered by functional effect onaugmenting T cell proliferation following the addition of monoclonalantibodies (Hutloff et al. (1999) Nature 397:263-266; Hansen et al.(1980) Immunogenics 10:247-260). Two cell surface glycoprotein ligandsfor PD-1 have been identified, PDL1 and PD-L2, and have been shown todownregulate T cell activation and cytokine secretion upon binding toPD-1 (Freeman et al. (2000) J Exp Med 192:1027-34; Latchman et al.(2001) Nat Immunol 2:261-8; Carter et al. (2002) Eur J Immunol32:634-43; Ohigashi et al. (2005) Clin Cancer Res 11:2947-53). Both PDL1(B7-HI) and PDL2 (B7-DC) are B7 homologs that bind to PD-1 but do notbind to other CD28 family members (Blank et al. (2004). Expression ofPDL1 on the cell surface has also been shown to be upregulated throughIFN-γ stimulation.

PDL1 expression has been found in several murine and human cancers,including human lung, ovarian and colon carcinoma and various myelomas(Iwai et al. (2002) PNAS 99:12293-7; Ohigashi et al. (2005). Clin CancerRes 11:2947-53). Currently available results reveal that PDL1overexpressed in tumor cells plays a key role in tumor immunity escapeby increasing apoptosis of T-cells. Researchers found that P815 tumorcell line transfected with PDL1 gene can be resistant to specific lysisby CTL, and has increased oncogenicity and invasive activity. Thesebiological activities can be reversed by blocking PDL1. Tumor cellstransplanted into mice with PDL1 knocked out to block PDL1/PD-1interaction, cannot form tumors (Dong et al. (2002) Nat Med 8:793-800).It has also been suggested that PDL1 might be involved in intestinalmucosal inflammation and inhibition of PDL1 suppresses wasting diseaseassociated with colitis (Kanai et al. (2003) J Immunol 171:4156-63).

There is still a need in the art for anti-PDL1 antibody which can bindto PDL1 with high affinity and be capable of blocking the binding ofPDL1 to PD-1 and, especially a heavy chain single domain antibodyagainst PDL1.

BRIEF DESCRIPTION OF THE INVENTION

The present inventors have obtained anti-PDL1 heavy chain single domainantibody (VHH) with high specificity, high affinity and high stabilityby screening with phage display technology.

In a first aspect, the invention provides a PDL1-binding moleculecomprising immunoglobulin single variable domain consisting of an aminoacid sequence selected from SEQ ID Nos: 1-6 and a human immunoglobulinFc region.

In another aspect, the present invention relates to a nucleic acidmolecule encoding the PDL1-binding molecule, and an expression vectorand host cell containing said nucleic acid molecule.

The present invention further relates to a pharmaceutical compositioncomprising the PDL1-binding molecule of the invention.

The present invention further relates to a method for producing thePDL1-binding molecule of the invention.

The present invention further relates to use of the PDL1-bindingmolecule, and pharmaceutical composition of the invention, especiallythe use and method for preventing and/or treating PDL1 relatingdiseases.

DESCRIPTION OF DRAWINGS

FIG. 1. shows the blocking effect of PDL1 heavy chain single domainantibodies to PD1/PDL1 interaction.

FIG. 2. shows the binding curves of PDL1 heavy chain single domainantibodies to PDL1 antigen protein.

FIG. 3. shows the blocking curves of PDL1 heavy chain single domainantibodies to PD1/PDL1 interaction.

FIG. 4. shows the sequence alignment of five humanized variants ofantibody No. 5.

FIG. 5. shows the binding curves of PDL1 single domain antibody-Fcfusion proteins to PDL1 (by ELISA).

FIG. 6. shows the blocking curves of PDL1 single domain antibody-Fcfusion proteins to PD1/PDL1 interaction (by competitive ELISA).

FIG. 7. shows the blocking curves of PDL1 single domain antibody-Fcfusion proteins to CD80/PDL1 interaction (by competitive ELISA).

FIG. 8. shows the blocking curves of PDL1 single domain antibody-Fcfusion proteins to PD1/293-PDL1 interaction (by FACS).

FIG. 9. shows the blocking curves of PDL1 single domain antibody-Fcfusion proteins to Jurket-PD1/PDL1 interaction (by FACS).

FIG. 10. shows the binding specificity of PDL1 single domain antibody-Fcfusion proteins to PDL1 protein detected by flow cytometry.

FIG. 11. shows the binding of PDL1 single domain antibody-Fc fusionproteins to monkey PDL1 protein detected by flow cytometry.

FIG. 12. shows that PDL1 single domain antibody-Fc fusion proteinsidentify PDL1 positive cell population on the tissue sections frompatients.

FIG. 13. shows the activation of PBMC by PDL1 single domain antibody-Fcfusion proteins.

FIG. 14. shows the activation of CD4+T cells by PDL1 single domainantibody-Fc fusion proteins.

FIG. 15. shows that PDL1 single domain antibody-Fc fusion proteinspromote the secretion of IL-2.

FIG. 16. shows the CDC and ADCC activities of the PDL1 single domainantibody-Fc fusion proteins carrying mutated Fc.

FIG. 17. shows the tumor growth curves after treatment with PDL1 singledomain antibody-Fc fusion proteins.

FIG. 18. shows the inhibition of tumor growth by administering PDL1single domain antibody-Fc fusion proteins for various times.

FIG. 19. shows the comparison between the tumor growth inhibitoryactivities of hu56V2-Fc and 2.41. A, A375:PBMC=5:1; B, A375:PBMC=1:1.

FIG. 20. shows the influence of alkali and oxidation treatments to theactivity of PDL1 single domain antibody-Fc fusion proteins.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Unless indicated or defined otherwise, all terms used have their usualmeaning in the art, which will be clear to the skilled person. Referenceis for example made to the standard handbooks, such as Sambrook et al,“Molecular Cloning: A Laboratory Manual” (2nd Ed.), Vols. 1-3. ColdSpring Harbor Laboratory Press (1989); Lewin, “Genes IV”, OxfordUniversity Press, New York, (1990), and Roitt et al., “Immunology” (2ndEd.), Gower Medical Publishing, London, New York (1989), as well as tothe general background art cited herein. Furthermore, unless indicatedotherwise, all methods, steps, techniques and manipulations that are notspecifically described in detail can be performed and have beenperformed in a manner known per se, as will be clear to the skilledperson. Reference is for example again made to the standard handbooks,to the general background art referred to above and to the furtherreferences cited therein.

Unless indicated otherwise, the interchangeable terms “antibody” and“immunoglobulin”—whether used herein to refer to a heavy chain antibodyor to a conventional 4-chain antibody—are used as general terms toinclude both the full-size antibody, the individual chains thereof, aswell as all parts, domains or fragments thereof (including but notlimited to antigen-binding domains or fragments such as VHH domains orVH/VL domains, respectively). In addition, the term “sequence” as usedherein (for example in terms like “immunoglobulin sequence”, “antibodysequence”, “(single) variable domain sequence”, “VHH sequence” or“protein sequence”), should generally be understood to include both therelevant amino acid sequence as well as nucleic acid sequences ornucleotide sequences encoding the same, unless the context requires amore limited interpretation.

The term “domain” (of a polypeptide or protein) as used herein refers toa folded protein structure which has the ability to retain its tertiarystructure independently of the rest of the protein. Generally, domainsare responsible for discrete functional properties of proteins, and inmany cases may be added, removed or transferred to other proteinswithout loss of function of the remainder of the protein and/or of thedomain.

The term “immunoglobulin domain” as used herein refers to a globularregion of an antibody chain (such as e.g. a chain of a conventional4-chain antibody or of a heavy chain antibody), or to a polypeptide thatessentially consists of such a globular region. Immunoglobulin domainsare characterized in that they retain the immunoglobulin foldcharacteristic of antibody molecules, which consists of a 2-layersandwich of about 7 antiparallel beta-strands arranged in twobeta-sheets, optionally stabilized by a conserved disulphide bond.

The term “immunoglobulin variable domain” as used herein means animmunoglobulin domain essentially consisting of four “framework regions”which are referred to in the art and hereinbelow as “framework region 1”or “FR1”; as “framework region 2” or “FR2”; as “framework region 3” or“FR3”; and as “framework region 4” or “FR4”, respectively; whichframework regions are interrupted by three “complementarity determiningregions” or “CDRs”, which are referred to in the art and hereinbelow as“complementarity determining region” or “CDR1”; as “complementaritydetermining region 2” or “CDR2”; and as “complementarity determiningregion 3” or “CDR3”, respectively. Thus, the general structure orsequence of an immunoglobulin variable domain can be indicated asfollows: FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4. It is the immunoglobulinvariable domain(s) that confer specificity to an antibody for theantigen by carrying the antigen-binding site.

The term “immunoglobulin single variable domain” as used herein means animmunoglobulin variable domain which is capable of specifically bindingto an epitope of the antigen without pairing with an additional variableimmunoglobulin domain. One example of immunoglobulin single variabledomains in the meaning of the present invention is “domain antibody”,such as the immunoglobulin single variable domains VH and VL (VH domainsand VL domains). Another example of immunoglobulin single variabledomains is “VHH domain” (or simply “VHH”) from camelids, as definedhereinafter.

“VHH domains”, also known as heavy chain single domain antibodies, VHHs,V_(H)H domains, VHH antibody fragments, and VHH antibodies, are theantigen binding immunoglobulin variable domain of “heavy chainantibodies” (i.e., “antibodies devoid of light chains”)(Hamers-Casterman C, Atarhouch T, Muyldermans S, Robinson G Hamers C,Songa E B, Bendahman N, Hamers R.: “Naturally occurring antibodiesdevoid of light chains”; Nature 363, 446-448 (1993)). The term “VHHdomain” has been chosen in order to distinguish these variable domainsfrom the heavy chain variable domains that are present in conventional4-chain antibodies (which are referred to herein as “VH domains”) andfrom the light chain variable domains that are present in conventional4-chain antibodies (which are referred to herein as “VL domains”). VHHdomains can specifically bind to an epitope without an additionalantigen binding domain (as opposed to VH or VL domains in a conventional4-chain antibody, in which case the epitope is recognized by a VL domaintogether with a VH domain). VHH domains are small, robust and efficientantigen recognition units formed by a single immunoglobulin domain.

In the context of the present invention, the terms heavy chain singledomain antibody, VHH domain. VHH, V_(H)H domain, VHH antibody fragment,VHH antibody, as well as “Nanobody®” and “Nanobody® domain” (“Nanobody”being a trademark of the company Ablynx N.V.; Ghent; Belgium) are usedinterchangeably.

The amino acid residues of VHH domains from Camelids are numberedaccording to the general numbering for VH domains given by Kabat et al.(“Sequence of proteins of immunological interest”, US Public HealthServices, NIH Bethesda, Md., Publication No. 91), as shown e.g. in FIG.2 of Riechmann and Muyldermans, J. Immunol. Methods 231, 25-38 (1999).According to this numbering.

-   -   FR1 comprises the amino acid residues at positions 1-30,    -   CDR1 comprises the amino acid residues at positions 31-35,    -   FR2 comprises the amino acids at positions 36-49,    -   CDR2 comprises the amino acid residues at positions 50-65,    -   FR3 comprises the amino acid residues at positions 66-94,    -   CDR3 comprises the amino acid residues at positions 95-102, and    -   FR4 comprises the amino acid residues at positions 103-113.

However, it should be noted that—as is well known in the art for VHdomains and for VHH domains—the total number of amino acid residues ineach of the CDRs may vary and may not correspond to the total number ofamino acid residues indicated by the Kabat numbering (that is, one ormore positions according to the Kabat numbering may not be occupied inthe actual sequence, or the actual sequence may contain more amino acidresidues than the number allowed for by the Kabat numbering). This meansthat, generally, the numbering according to Kabat may or may notcorrespond to the actual numbering of the amino acid residues in theactual sequence.

Alternative methods for numbering the amino acid residues of VH domains,which methods can also be applied in an analogous manner to VHH domains,are known in the art. However, in the present description, claims andfigures, the numbering according to Kabat and applied to VHH domains asdescribed above will be followed, unless indicated otherwise.

The total number of amino acid residues in a VHH domain will usually bein the range of from 110 to 120, often between 112 and 115. It shouldhowever be noted that smaller and longer sequences may also be suitablefor the purposes described herein.

Further structural characteristics and functional properties of VHHdomains and polypeptides containing the same can be summarized asfollows:

VHH domains (which have been “designed” by nature to functionally bindto an antigen without the presence of, and without any interaction with,a light chain variable domain) can function as a single, relativelysmall, functional antigen-binding structural unit, domain orpolypeptide. This distinguishes the VHH domains from the VH and VLdomains of conventional 4-chain antibodies, which by themselves aregenerally not suitable for practical application as singleantigen-binding proteins or immunoglobulin single variable domains, butneed to be combined in some form or another to provide a functionalantigen-binding unit (as in for example conventional antibody fragmentssuch as Fab fragments; in scFvs, which consist of a VH domain covalentlylinked to a VL domain).

Because of these unique properties, the use of VHH domains—either aloneor as part of a larger polypeptide—offers a number of significantadvantages over the use of conventional VH and VL domains, scFvs orconventional antibody fragments (such as Fab- or F(ab′)₂-fragments):

-   -   only a single domain is required to bind an antigen with high        affinity and with high selectivity, so that there is no need to        have two separate domains present, nor to assure that these two        domains are present in the right spatial conformation and        configuration (i.e. through the use of especially designed        linkers, as with scFvs);    -   VHH domains can be expressed from a single gene and require no        post-translational folding or modifications;    -   VHH domains can easily be engineered into multivalent and        multispecific formats (formatted);    -   VHH domains are highly soluble and do not have a tendency to        aggregate;    -   VHH domains are highly stable to heat, pH, proteases and other        denaturing agents or conditions and, thus, may be prepared,        stored or transported without the use of refrigeration        equipments, conveying a cost, time and environmental savings;    -   VHH domains are easy and relatively cheap to prepare, even on a        scale required for production;    -   VHH domains are relatively small (approximately 15 kDa, or 10        times smaller than a conventional IgG) compared to conventional        4-chain antibodies and antigen-binding fragments thereof, and        therefore show high(er) penetration into tissues and can be        administered in higher doses than such conventional 4-chain        antibodies and antigen-binding fragments thereof;    -   VHH domains can show so-called cavity-binding properties        (especially due to their extended CDR3 loop, compared to        conventional VH domains) and can therefore also access targets        and epitopes not accessible to conventional 4-chain antibodies        and antigen-binding fragments thereof.

Methods of obtaining VHH domains binding to a specific antigen orepitope have been described earlier, e.g. in WO2006/040153 andWO2006/122786; R. van der Linden et al., Journal of ImmunologicalMethods, 240 (2000) 185-195; Li et al., J Biol Chem., 287 (2012)13713-13721; Deffar et al., African Journal of Biotechnology Vol. 8(12), pp. 2645-2652, 17 June, 2009 and WO94/04678.

VHH domains derived from camelids can be “humanized” by replacing one ormore amino acid residues in the amino acid sequence of the original VHHsequence by one or more of the amino acid residues that occur at thecorresponding position(s) in a VH domain from a conventional 4-chainantibody from a human being. A humanized VHH domain can contain one ormore fully human framework region sequences, and in a specificembodiment, containing IGHV3 human framework region sequence.

Generally, the term “specificity” refers to the number of differenttypes of antigens or epitopes to which a particular antigen-bindingmolecule or antigen-binding protein (such as an immunoglobulin singlevariable domain of the invention) molecule can bind. The specificity ofan antigen-binding molecule can be determined based on its affinityand/or avidity. The affinity, represented by the equilibrium constantfor the dissociation of an antigen with an antigen-binding protein (KD),is a measure for the binding strength between an epitope and anantigen-binding site on the antigen-binding protein: the lesser thevalue of the KD, the stronger the binding strength between an epitopeand the antigen-binding molecule (alternatively, the affinity can alsobe expressed as the affinity constant (KA), which is 1/KD). As will beclear to the skilled person, affinity can be determined in a mannerknown per se, depending on the specific antigen of interest. Avidity isthe measure of the strength of binding between an antigen-bindingmolecule (such as an immunoglobulin, an antibody, an immunoglobulinsingle variable domain or a polypeptide containing it) and the pertinentantigen. Avidity is related to both the affinity between an epitope andits antigen binding site on the antigen-binding molecule and the numberof pertinent binding sites present on the antigen-binding molecule.

Typically, specific binding molecules will bind to PDL1 with adissociation constant (KD) of 10⁻⁷ to 10⁻¹¹ moles/liter (M), andpreferably 10⁻⁸ to 10⁻¹¹ moles/liter, more preferably 10⁻⁹ to 10⁻¹¹moles/liter, and even more preferably 10⁻¹⁰ to 10⁻¹¹ moles/liter or less(as measured in a Biacore or in a KinExA assay), and/or with anassociation constant (KA) of at least 10⁷ M⁻¹, preferably at least 10⁸M⁻¹, more preferably at least 10⁹ M⁻¹, more preferably at least 10¹⁰M⁻¹, such as at least 10¹⁰ M⁻¹. Any KD value greater than 10⁻⁴ M isgenerally considered to indicate non-specific binding. Specific bindingof an antigen-binding protein to an antigen or epitope can be determinedin any suitable manner known per se, including, for example, the assaysdescribed herein, Scatchard analysis and/or competitive binding assays,such as radioimmunoassays (RIA), enzyme immunoassays (EIA) and sandwichcompetition assays.

Amino acid residues will be indicated according to the standardthree-letter or one-letter amino acid code, as generally known andagreed upon in the art. When comparing two amino acid sequences, theterm “amino acid difference” refers to insertions, deletions orsubstitutions of the indicated number of amino acid residues at aposition of the reference sequence, compared to a second sequence. Incase of substitution(s), such substitution(s) will preferably beconservative amino acid substitution(s), which means that an amino acidresidue is replaced with another amino acid residue of similar chemicalstructure and which has little or essentially no influence on thefunction, activity or other biological properties of the polypeptide.Such conservative amino acid substitutions are well known in the art,wherein conservative amino acid substitutions preferably aresubstitutions in which one amino acid within the following groups(i)-(v) is substituted by another amino acid residue within the samegroup: (i) small aliphatic, nonpolar or slightly polar residues: Ala,Ser, Thr, Pro and Gly; (ii) polar, negatively charged residues and their(uncharged) amides: Asp, Asn, Glu and Gin; (iii) polar, positivelycharged residues: His, Arg and Lys; (iv) large aliphatic, nonpolarresidues: Met, Leu, He, Val and Cys; and (v) aromatic residues: Phe, Tyrand Trp. Particularly preferred conservative amino acid substitutionsare as follows: Ala into Gly or into Ser; Arg into Lys; Asn into Gln orinto His; Asp into Glu; Cys into Ser; Gln into Asn; Glu into Asp; Glyinto Ala or into Pro; His into Asn or into Gln; Ile into Leu or intoVal; Leu into Ile or into Val; Lys into Arg, into Gln or into Glu; Metinto Leu, into Tyr or into Ile; Phe into Met, into Leu or into Tyr; Serinto Thr; Thr into Ser; Trp into Tyr; Tyr into Trp or into Phe; Val intoIle or into Leu.

A polypeptide or nucleic acid molecule is considered to be “essentiallyisolated”—for example, when compared to its native biological sourceand/or the reaction medium or cultivation medium from which it has beenobtained—when it has been separated from at least one other componentwith which it is usually associated in said source or medium, such asanother protein/polypeptide, another nucleic acid, another biologicalcomponent or macromolecule or at least one contaminant, impurity orminor component. In particular, a polypeptide or nucleic acid moleculeis considered “essentially isolated” when it has been purified at least2-fold, in particular at least 10-fold, more in particular at least100-fold, and up to 1000-fold or more. A polypeptide or nucleic acidmolecule that is “in essentially isolated form” is preferablyessentially homogeneous, as determined using a suitable technique, suchas a suitable chromatographical technique, such as polyacrylamide gelelectrophoresis.

As used herein, the term “subject” refers to mammalian, especiallyprimate, in particular human.

PDL1 Binding Molecule of the Invention

In a first aspect, the invention provides an programmed death ligand 1(PDL1)-binding molecule, which can specifically bind to PDL1 andconsists of an amino acid sequence as shown in formula A-L-B, wherein Arepresents an immunoglobulin single variable domain, L is absent orrepresents an amino acid linker, and B represents an humanimmunoglobulin Fc region,

wherein the immunoglobulin single variable domain consisting of an aminoacid sequence selected from SEQ ID NOs:1-6,

said PDL1-binding molecule is capable of forming homodimers via saidhuman immunoglobulin Fc region.

As used herein, “human immunoglobulin Fc region” refers to an Fc regionfrom constant region of human IgG1, IgG2, IgG3 or IgG4 (amino acidsequences of the constant regions refer to Items P01857, P01859, P01860,P01861 in www.uniprot.org protein database), which comprises a Hingeregion or part of the hinge region, CH2 region, and CH3 region ofimmunoglobulin constant region. In the present invention, ADCC or CDCactivity may be increased or removed, or the affinity of FcRn may beincreased or decreased, by mutating 1-5 amino acids in CH2 region of theamino acid sequence of the “human immunoglobulin Fc region”; or proteinstability can be increased by mutating 1-4 amino acids in the hingeregion. However, in the present invention, “human immunoglobulin Fcregion” does not include any mutation that promotes or prevents theformation of Fc heterodimers, nor any modification of adding otherfunctional protein sequence to N-terminal or C-terminal to the Fcfragment.

In a preferred embodiment, said immunoglobulin Fc region is mutated toremove ADCC and CDC activities. In a specific embodiment, the sequenceof said immunoglobulin Fc region is selected from SEQ ID NOs:7-9.

A person skilled in the art will understand that PDL1-binding moleculeof the present invention will generally present in the form ofhomodimers due to the human immunoglobulin Fc region.

As used herein, the term “linker” means a non-functional amino acidsequence of 1-20 amino acid residues in length, without secondary orhigher structures. For example, said linker is a flexible linker, suchas GGGS, GS, GAP and the like.

In some embodiments, the PDL1-binding molecule of the invention consistsof an amino acid sequence selected from SEQ ID NOs:10-27.

The PDL1-binding molecule of the invention has at least one of thefollowing features:

(a) binding to human PDL1 with a KD of less than 1×10⁻⁷ M:

(b) blocking the interaction between PDL1 and PD-1:

(c) enhancing activation of PBMCs and/or T cells;

(d) inhibiting tumor growth.

The PDL1-binding molecule of the invention may bind to PDL1 with a KD ofless than 1×10⁻⁷ M, preferably less than 1×10⁻⁸ M, more preferably lessthan 1×10⁻⁹ M, more preferably less than 1×10⁻¹⁰ M, and even morepreferably less than 1×10⁻¹¹ M.

In some embodiments, the PDL1-binding molecule of the invention canspecifically bind to human PDL1 and block the interaction between PDL1and PD-1. In some embodiments, the PDL1-binding molecule of theinvention can specifically bind to human PDL1 and block the interactionbetween PDL1 and CD80.

The PDL1-binding molecule of the invention can inhibit tumor growth byat least about 10%, preferably at least about 20%, more preferably atleast about 30%, more preferably at least about 40%, more preferably atleast about 50%, more preferably at least about 60%, more preferably atleast about 70%, and more preferably at least about 80%.

Furthermore, the PDL1-binding molecule of the invention is resistant toalkali treatment and oxidation treatment. For example, the PDL1-bindingmolecule of the invention maintains its activity after treatment withstrong base (such as 500 mM ammonium bicarbonate) for about 8 hours,preferably about 16 hours, more preferably about 24 hours or morepreferably about 32 hours. Alternatively, the PDL1-binding molecule ofthe invention maintains its activity after treatment with oxidant (1%hydrogen peroxide) for about 2 hours, preferably about 4 hours, or morepreferably about 8 hours.

In addition, the PDL1-binding molecule of the invention is stable athigh concentration. For example, the PDL1-binding molecule of theinvention keeps stable at a concentration of about 100 mg/ml, morepreferably about 150 mg/ml, more preferably about 200 mg/ml or morepreferably about 250 mg/ml without forming aggregates.

Nucleic Acid, Vector and Host Cell

In another aspect, the invention relates to nucleic acid molecule thatencodes the PDL1-binding molecules of the invention. A nucleic acid ofthe invention may be RNA, DNA or cDNA. According to one embodiment ofthe invention, the nucleic acid of the invention is in essentiallyisolated form.

The nucleic acid of the invention may also be in the form of, may bepresent in and/or may be part of a vector, such as for example aplasmid, cosmid or YAC. The vector may especially be an expressionvector, i.e. a vector that can provide for expression of thePDL1-binding molecule in vitro and/or in vivo (i.e. in a suitable hostcell, host organism and/or expression system). Such expression vectorgenerally comprises at least one nucleic acid of the invention that isoperably linked to one or more suitable regulatory elements, such aspromoter(s), enhancer(s), terminator(s), and the like. Such elements andtheir selection in view of expression of a specific sequence in aspecific host are common knowledge of the skilled person. Specificexamples of regulatory elements and other elements useful or necessaryfor expressing PDL1-binding molecules of the invention include such aspromoters, enhancers, terminators, integration factors, selectionmarkers, leader sequences, reporter genes, and the like.

The nucleic acids of the invention may be prepared or obtained in amanner known per se (e.g. by automated DNA synthesis and/or recombinantDNA technology), based on the information on the amino acid sequencesfor the polypeptides of the invention given herein, and/or can beisolated from a suitable natural source.

In another aspect, the invention relates to host cells that express orare capable of expressing one or more PDL1-binding molecule of theinvention; and/or that contain a nucleic acid of the invention.According to a particularly preferred embodiment, said host cells arebacterial cells; other useful cells are yeast cells, fungal cells ormammalian cells.

Suitable bacterial cells include cells from gram-negative bacterialstrains such as strains of Escherichia coli, Proteus, and Pseudomonas,and gram-positive bacterial strains such as strains of Bacillus,Streptomyces, Staphylococcus, and Lactococcus. Suitable fungal cellinclude cells from species of Trichoderma, Neurospora, and Aspergillus.

Suitable fungal cell include cells from species of Trichoderma,Neurospora, and Aspergillus. Suitable yeast cells include cells fromspecies of Saccharomyces (for example, Saccharomyces cerevisiae),Schizosaccharomyces (for example, Schizosaccharomyces pombe), Pichia(for example, Pichia pastoris and Pichia methanolica), and Hansenula.

Suitable mammalian cells include for example HEK293 cells, CHO cells,BHK cells, HeLa cells, COS cells, and the like.

However, amphibian cells, insect cells, plant cells, and any other cellsused in the art for the expression of heterologous proteins can be usedas well.

The invention further provides methods of manufacturing a PDL1-bindingmolecule of the invention, such methods generally comprise the steps of:

-   -   culturing host cells of the invention under conditions that        allow expression of the PDL1-binding molecule of the invention;        and    -   recovering the PDL1-binding molecule expressed by the host cells        from the culture; and    -   optionally further purifying and/or modifying the PDL1-binding        molecule of the invention.

In a preferred embodiment, the PDL1-binding molecule of the invention isproduced by using mammalian cells. The PDL1-binding molecule of theinvention can achieve high expression in mammalian cells. For example,the expression level can be up to about 5 g/L, preferably about 6 g/L,preferably about 7 g/L, preferably about 8 g/L, preferably about 9 g/L,preferably about 10 g/L or higher.

PDL1-binding molecules of the invention may be produced in a cell as setout above either intracellullarly (e.g. in the cytosol, in theperiplasma or in inclusion bodies) and then isolated from the host cellsand optionally further purified; or they can be produced extracellularly(e.g. in the medium in which the host cells are cultured) and thenisolated from the culture medium and optionally further purified.

Methods and reagents used for the recombinant production ofpolypeptides, such as specific suitable expression vectors,transformation or transfection methods, selection markers, methods ofinduction of protein expression, culture conditions, and the like, areknown in the art. Similarly, protein isolation and purificationtechniques useful in a method of manufacture of a PDL1-binding moleculeof the invention are well known to the skilled person.

However, the PDL1-binding molecules of the invention can also beobtained by other methods for production of proteins known in the art,such as, chemical synthesis, including solid phase or liquid phasesynthesis.

Pharmaceutical Compositions

In another aspect, the present invention provides a composition, e.g., apharmaceutical composition, containing one or a combination ofPDL1-binding molecule of the present invention, formulated together witha pharmaceutically acceptable carrier. Such compositions may include oneor a combination of (e.g., two or more different) PDL1-binding moleculesof the invention. A person skilled in the art will understand thatPDL1-binding molecule of the present invention will generally present inthe form of homodimer due to the human immunoglobulin Fc region.

Pharmaceutical compositions of the invention also can be administered incombination therapy, i.e., combined with other agents. For example, thecombination therapy can include a PDL1-binding molecule of the presentinvention combined with at least one other anti-tumor agent. Forexample, PDL1-binding molecule of the invention may be administered incombination with antibodies targeting other tumor-specific antigens.Said antibodies targeting other tumor-specific antigens include, but arenot limited to anti-EGFR antibody, anti-EGFR variant antibody,anti-VEGFa antibody, anti-HER2 antibody, or anti-CMET antibody.Preferably, said antibodies are monoclonal.

As used herein, “pharmaceutically acceptable carrier” includes any andall solvents, dispersion media, coatings, antibacterial and antifungalagents, isotonic and absorption delaying agents, and the like that arephysiologically compatible. Preferably, the carrier is suitable forintravenous, intramuscular, subcutaneous, parenteral, spinal orepidermal administration (e.g., by injection or infusion). Depending onthe route of administration, the active compound, i.e., antibody, orimmunoconjugate, may be coated in a material to protect the compoundfrom the action of acids and other natural conditions that mayinactivate the compound.

The pharmaceutical compounds of the invention may include one or morepharmaceutically acceptable salts. A “pharmaceutically acceptable salt”refers to a salt that retains the desired biological activity of theparent compound and does not impart any undesired toxicological effects(see e.g., Berge, S. M., et al. (1977) J. Pharm. Sci. 66:1-19). Examplesof such salts include acid addition salts and base addition salts. Acidaddition salts include those derived from nontoxic inorganic acids, suchas hydrochloric, nitric, phosphoric, sulfuric, hydrobromic, hydroiodic,phosphorous and the like, as well as from nontoxic organic acids such asaliphatic mono- and dicarboxylic acids, phenyl-substituted alkanoicacids, hydroxy alkanoic acids, aromatic acids, aliphatic and aromaticsulfonic acids and the like. Base addition salts include those derivedfrom alkaline earth metals, such as sodium, potassium, magnesium,calcium and the like, as well as from nontoxic organic amines, such asN,N′-dibenzylethylenediamine, N-methylglucamine, chloroprocaine,choline, diethanolamine, ethylenediamine, procaine and the like.

A pharmaceutical composition of the invention also may include apharmaceutically acceptable anti-oxidant. Examples of pharmaceuticallyacceptable antioxidants include: (1) water soluble antioxidants, such asascorbic acid, cysteine hydrochloride, sodium bisulfate, sodiummetabisulfite, sodium sulfite and the like; (2) oil-solubleantioxidants, such as ascorbyl palmitate, butylated hydroxyanisole(BHA), butylated hydroxytoluene (BHT), lecithin, propyl gallate,alpha-tocopherol, and the like; and (3) metal chelating agents, such ascitric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol, tartaricacid, phosphoric acid, and the like.

These compositions may also contain adjuvants such as preservatives,wetting agents, emulsifying agents and dispersing agents.

Prevention of presence of microorganisms may be ensured both bysterilization procedures, supra, and by the inclusion of variousantibacterial and antifungal agents, for example, paraben,chlorobutanol, phenol sorbic acid, and the like. It may also bedesirable to include isotonic agents, such as sugars, sodium chloride,and the like into the compositions. In addition, prolonged absorption ofthe injectable pharmaceutical form may be brought about by the inclusionof agents which delay absorption such as aluminum monostearate andgelatin.

Pharmaceutically acceptable carriers include sterile aqueous solutionsor dispersions and sterile powders for the extemporaneous preparation ofsterile injectable solutions or dispersion. The use of such media andagents for pharmaceutically active substances is known in the art.Except insofar as any conventional media or agent is incompatible withthe active compound, use thereof in the pharmaceutical compositions ofthe invention is contemplated. Supplementary active compounds can alsobe incorporated into the compositions.

Therapeutic compositions typically must be sterile and stable under theconditions of manufacture and storage. The composition can be formulatedas a solution, microemulsion, liposome, or other ordered structuresuitable to high drug concentration. The carrier can be a solvent ordispersion medium containing, for example, water, ethanol, polyol (forexample, glycerol, propylene glycol, and liquid polyethylene glycol, andthe like), and suitable mixtures thereof. The proper fluidity can bemaintained, for example, by the use of a coating such as lecithin, bythe maintenance of the required particle size in the case of dispersionand by the use of surfactants.

Sterile injectable solutions can be prepared by incorporating the activecompound in the required amount in an appropriate solvent with one or acombination of ingredients enumerated above, as required, followed bysterilization microfiltration. Generally, dispersions are prepared byincorporating the active compound into a sterile vehicle that contains abasic dispersion medium and the required other ingredients from thoseenumerated above. In the case of sterile powders for the preparation ofsterile injectable solutions, the preferred methods of preparation arevacuum drying and freeze-drying (lyophilization) that yield a powder ofthe active ingredient plus any additional desired ingredient from apreviously sterile-filtered solution thereof.

The amount of active ingredient which can be combined with a carriermaterial to produce a single dosage form will vary depending upon thesubject being treated, and the particular mode of administration. Theamount of active ingredient which can be combined with a carriermaterial to produce a single dosage form will generally be that amountof the composition which produces a therapeutic effect. Generally, outof one hundred percent, this amount will range from about 0.01 percentto about ninety-nine percent of active ingredient, preferably from about0.1 percent to about 70 percent, most preferably from about 1 percent toabout 30 percent of active ingredient in combination with apharmaceutically acceptable carrier.

Dosage regimens are adjusted to provide the optimum desired response(e.g., a therapeutic response). For example, a single bolus may beadministered, several divided doses may be administered over time or thedose may be proportionally reduced or increased as indicated by theexigencies of the therapeutic situation. It is especially advantageousto formulate parenteral compositions in dosage unit form for ease ofadministration and uniformity of dosage. Dosage unit form as used hereinrefers to physically discrete units suited as unitary dosages for thesubjects to be treated; each unit contains a predetermined quantity ofactive compound calculated to produce the desired therapeutic effect inassociation with the required pharmaceutical carrier. The specificationfor the dosage unit forms of the invention are dictated by and directlydependent on (a) the unique characteristics of the active compound andthe particular therapeutic effect to be achieved, and (b) thelimitations inherent in the art of compounding such an active compoundfor the treatment of sensitivity in individuals.

For administration of the antibody molecule, the dosage ranges fromabout 0.0001 to 100 mg/kg, and more usually 0.01 to 5 mg/kg, of thesubject body weight. For example dosages can be 0.3 mg/kg body weight, 1mg/kg body weight, 3 mg/kg body weight, 5 mg/kg body weight. 10 mg/kgbody weight or 20 mg/kg body weight or within the range of 1-20 mg/kg.An exemplary treatment regime entails administration once per week, onceevery two weeks, once every three weeks, once every four weeks, once amonth, once every 3 months or once every three to 6 months, or with ashort administration interval at the beginning (such as once per week toonce every three weeks), and then an extended interval later (such asonce a month to once every three to 6 months).

Alternatively, antibody can be administered as a sustained releaseformulation, in which case less frequent administration is required.Dosage and frequency vary depending on the half-life of the antibody inthe patient. In general, human antibodies show the longest half life,followed by humanized antibodies, chimeric antibodies, and nonhumanantibodies. The dosage and frequency of administration can varydepending on whether the treatment is prophylactic or therapeutic. Inprophylactic applications, a relatively low dosage is administered atrelatively infrequent intervals over a long period of time. Somepatients continue to receive treatment for the rest of their lives. Intherapeutic applications, a relatively high dosage at relatively shortintervals is sometimes required until progression of the disease isreduced or terminated, and preferably until the patient shows partial orcomplete amelioration of symptoms of disease. Thereafter, the patientcan be administered a prophylactic regime.

Actual dosage levels of the active ingredients in the pharmaceuticalcompositions of the present invention may be varied so as to obtain anamount of the active ingredient which is effective to achieve thedesired therapeutic response for a particular patient, composition, andmode of administration, without being toxic to the patient. The selecteddosage level will depend upon a variety of pharmacokinetic factorsincluding the activity of the particular compositions of the presentinvention employed, or the ester, salt or amide thereof, the route ofadministration, the time of administration, the rate of excretion of theparticular compound being employed, the duration of the treatment, otherdrugs, compounds and/or materials used in combination with theparticular compositions employed, the age, sex, weight, condition,general health and prior medical history of the patient being treated,and like factors well known in the medical arts.

A “therapeutically effective amount” of a PDL1-binding molecule of theinvention preferably results in a decrease in severity of diseasesymptoms, an increase in frequency and duration of disease symptom-freeperiods, or a prevention of impairment or disability due to the diseaseaffliction. For example, for the treatment of PDL1 relating tumors, a“therapeutically effective amount” preferably inhibits cell growth ortumor growth by at least about 10%, at least about 20%, more preferablyby at least about 40%, even more preferably by at least about 60%, andstill more preferably by at least about 80% relative to untreatedsubjects. The ability to inhibit tumor growth can be evaluated in ananimal model system predictive of efficacy in human tumors.Alternatively, this property of a composition can be evaluated byexamining the ability of the compound to inhibit cell growth; suchinhibition can be determined in vitro by assays known to the skilledpractitioner. A therapeutically effective amount of a therapeuticcompound can decrease tumor size, or otherwise ameliorate symptoms in asubject. One of ordinary skill in the art would be able to determinesuch amounts based on such factors as the subject's size, the severityof the subject's symptoms, and the particular composition or route ofadministration selected.

A composition of the present invention can be administered via one ormore routes of administration using one or more of a variety of methodsknown in the art. As will be appreciated by the skilled artisan, theroute and/or mode of administration will vary depending upon the desiredresults. Preferred routes of administration for PDL1-binding moleculesof the invention include intravenous, intramuscular, intradermal,intraperitoneal, subcutaneous, spinal or other parenteral routes ofadministration, for example by injection or infusion. The phrase“parenteral administration” as used herein means modes of administrationother than enteral and topical administration, usually by injection, andincludes, without limitation, intravenous, intramuscular, intraarterial,intrathecal, intracapsular, intraorbital, intracardiac, intradermal,intraperitoneal, transtracheal, subcutaneous, subcuticular,intraarticular, subcapsular, subarachnoid, intraspinal, epidural andintrasternal injection and infusion.

Alternatively, a PDL1-binding molecule of the invention can beadministered via a non-parenteral route, such as a topical, epidermal ormucosal route of administration, for example, intranasally, orally,vaginally, rectally, sublingually or topically.

The active compounds can be prepared with carriers that will protect thecompound against rapid release, such as a controlled releaseformulation, including implants, transdermal patches, andmicroencapsulated delivery systems. Biodegradable, biocompatiblepolymers can be used, such as ethylene vinyl acetate, polyanhydrides,polyglycolic acid, collagen, polyorthoesters, and polylactic acid. Manymethods for the preparation of such formulations are patented orgenerally known to those skilled in the art. See, e.g., Sustained andControlled Release Drug Delivery Systems, J. R. Robinson, ed., MarcelDekker, Inc., New York, 1978.

Therapeutic compositions can be administered with medical devices knownin the art. For example, in a preferred embodiment, a therapeuticcomposition of the invention can be administered with a needlelesshypodermic injection device, such as the devices disclosed in U.S. Pat.Nos. 5,399,163; 5,383,851; 5,312,335; 5,064,413; 4,941,880; 4,790,824;or 4,596,556. Examples of well-known implants and modules useful in thepresent invention include: U.S. Pat. No. 4,487,603, which discloses animplantable micro-infusion pump for dispensing medication at acontrolled rate; U.S. Pat. No. 4,486,194, which discloses a therapeuticdevice for administering medicaments through the skin; U.S. Pat. No.4,447,233, which discloses a medication infusion pump for deliveringmedication at a precise infusion rate; U.S. Pat. No. 4,447,224, whichdiscloses a variable flow implantable infusion apparatus for continuousdrug delivery; U.S. Pat. No. 4,439,196, which discloses an osmotic drugdelivery system having multi-chamber compartments; and U.S. Pat. No.4,475,196, which discloses an osmotic drug delivery system. Thesepatents are incorporated herein by reference. Many other such implants,delivery systems, and modules are known to those skilled in the art.

In certain embodiments, the PDL1-binding molecules of the invention canbe formulated to ensure proper distribution in vivo. For example, theblood-brain barrier (BBB) excludes many highly hydrophilic compounds. Toensure that the therapeutic compounds of the invention cross the BBB (ifdesired), they can be formulated, for example, in liposomes. For methodsof manufacturing liposomes, see, e.g., U.S. Pat. Nos. 4,522,811;5,374,548; and 5,399,331. The liposomes may comprise one or moremoieties which are selectively transported into specific cells ororgans, thus enhance targeted drug delivery (see, e.g., V. V. Ranade(1989) J. Clin. Pharmacol. 29:685). Exemplary targeting moieties includefolate or biotin (see, e.g., U.S. Pat. No. 5,416,016 to Low et al);mannosides (Umezawa et al., (1988) Biochem. Biophys. Res. Commun.153:1038): antibodies (P. G. Bloeman et al. (1995) FEBS Lett. 357:140;M. Owais et al. (1995) Antimicrob. Agents Chemother. 39:180); surfactantprotein A receptor (Briscoe et al. (1995) Am. J. Physiol. 1233; 134); p120 (Schreier et al. (1994) J Biol. Chem. 269:9090): see also K.Keinanen; M. L. Laukkanen (1994) FEBS Lett. 346:123; J J. Killion; L J.Fidler (1994) Immunomethods 4:273.

Preventing and Treating of Diseases

In another aspect, the present invention provides the use of the PDL1binding molecule, nucleic acid, host cell, and pharmaceuticalcomposition of the invention for preventing and/or treating PDL1relating diseases, as well as the corresponding methods. PDL1 relatingdiseases that can be prevented and/or treated with the PDL1 bindingmolecule of the invention are described in detailed as follows.

Cancer

Blocking PDL1 by PDL1-binding molecule of the invention can enhance theimmune response to cancerous cells in the patient. PDL1 is not expressedin normal human cells, but is abundant in a variety of human cancers(Dong et al. (2002) Nat Med 8:787-9). The interaction between PD-1 andPDL1 results in a decrease in tumor infiltrating lymphocytes, a decreasein T-cell receptor mediated proliferation, and immune evasion by thecancerous cells (Dong et al. (2003) J Mol Med 81:281-7; Blank et al.(2004) Cancer Immunol. Immunother. [epub]; Konishi et al. (2004) Clin.Cancer Res. 10:5094-100). Immune suppression can be reversed byinhibiting the local interaction of PDL1 to PD-1 and the effect isadditive when the interaction of PD-L2 to PD-1 is blocked as well (Iwaiet al. (2002) PNAS 99:12293-7; Brown et al. (2003) J. Immunol. JTO:1257-66). A PDL1-binding molecule of the invention may be used alone toinhibit the growth of cancerous tumors. Alternatively, a PDL1-bindingmolecule of the invention may be used in conjunction with otherimmunogenic agents, standard cancer treatments, or other antibodies, asdescribed below.

Accordingly, in one embodiment, the invention provides a method ofpreventing or treating cancer in a subject, comprising administering tothe subject a therapeutically effective amount of PDL1-binding moleculeof the invention so as to inhibit growth of tumor cells in the subject.

Preferred cancers whose growth may be inhibited using the antibodies ofthe invention include cancers typically responsive to immunotherapy.Non-limiting examples of preferred cancers for treatment include lungcancer, ovarian cancer, colon cancer, rectal cancer, melanoma (e.g.,metastatic malignant melanoma), renal cancer, bladder cancer, breastcancer, liver cancer, lymphoma, hematological malignancy, head and neckcancer, glioma, gastric cancer, nasopharyngeal cancer, laryngeal cancer,cervical cancer, corpus carcinoma, osteosarcoma. Examples of othercancers that may be treated using the methods of the invention includebone cancer, pancreatic cancer, prostatic cancer, skin cancer, cancer ofthe head or neck, cutaneous or intraocular malignant melanoma, uterinecancer, cancer of the anal region, testicular cancer, carcinoma of thefallopian tubes, carcinoma of the endometrium, carcinoma of the cervix,carcinoma of the vagina, carcinoma of the vulva, Hodgkin's Disease,non-Hodgkin's lymphoma, cancer of the esophagus, cancer of the smallintestine, cancer of the endocrine system, cancer of the thyroid gland,cancer of the parathyroid gland, cancer of the adrenal gland, sarcoma ofsoft tissue, cancer of the urethra, cancer of the penis, chronic oracute leukemia including acute myeloid leukemia, chronic myeloidleukemia, acute lymphoblastic leukemia, chronic lymphocytic leukemia,solid tumors of childhood, lymphocytic lymphoma, cancer of the bladder,cancer of the kidney or ureter, carcinoma of the renal pelvis, neoplasmof the central nervous system (CNS), primary CNS lymphoma, tumorangiogenesis, spinal axis tumor, brain stem glioma, pituitary adenoma,Kaposi's sarcoma, epidermoid cancer, squamous cell cancer, T-celllymphoma, environmentally induced cancers including those induced byasbestos, and combinations of said cancers. The present invention isalso useful for treatment of metastatic cancers, especially metastaticcancers that express PDL1 (Iwai et al. (2005) Int. Immunol. 17:133-144).

Optionally, PDL1-binding molecule of the invention can be combined withan immunogenic agent, such as cancerous cells, purified tumor antigens(including recombinant proteins, peptides, and carbohydrate molecules),cells, and cells transfected with genes encoding immune stimulatingcytokines (He et al. (2004) J. Immunol. 173:4919-28). Non-limitingexamples of tumor vaccines that can be used include peptides of melanomaantigens, such as peptides of gp100, MAGE antigens, Trp-2, MARTI and/ortyrosinase, or tumor cells transfected to express the cytokine GM-CSF.

In humans, some tumors have been shown to be immunogenic such asmelanomas. It is anticipated that by raising the threshold of T cellactivation by PDL1 blockade with PDL1-binding molecule of the invention,it is possible to activate tumor responses in the host. PDL1 blockade(such as PDL1 antibody, e.g., the PDL1-binding molecule of theinvention) is likely to be most effective when combined with avaccination protocol. Many experimental strategies for vaccinationagainst tumors have been devised (see Rosenberg, S., 2000, Developmentof Cancer Vaccines, ASCO Educational Book Spring: 60-62; Logothetis, C,2000, ASCO Educational Book Spring: 300-302; Khayat, D. 2000, ASCOEducational Book Spring: 414-428; Foon, K. 2000, ASCO Educational BookSpring: 730-738; see also Restifo, N. and Sznol, M., Cancer Vaccines,Ch. 61, pp. 3023-3043 in DeVita, V. et al. (eds.). 1997, Cancer:Principles and Practice of Oncology. Fifth Edition). In one of thesestrategies, a vaccine is prepared using autologous or allogeneic tumorcells. These cellular vaccines have been shown to be most effective whenthe tumor cells are transduced to express GM-CSF. GM-CSF has been shownto be a potent activator of antigen presentation for tumor vaccination(Dranoff et al. (1993) Proc. Natl. Acad. Sd U.S.A. 90: 3539-43).

The study of gene expression and large scale gene expression patterns invarious tumors has led to the definition of so-called tumor specificantigens (Rosenberg. SA (1999) Immunity 10: 281-7). In many cases, thesetumor specific antigens are differentiation antigens expressed in thetumors and in the cell from which the tumor arose, for examplemelanocyte antigens gp100, MAGE antigens, and Trp-2. More importantly,many of these antigens can be shown to be the targets of tumor specificT cells found in the host. PDL1-binding molecule of the invention may beused in conjunction with a collection of recombinant proteins and/orpeptides expressed in a tumor in order to generate an immune response tothese proteins. These proteins are normally viewed by the immune systemas self antigens and are therefore tolerant to them. The tumor antigenmay also include the protein telomerase, which is required for thesynthesis of telomeres of chromosomes and which is expressed in morethan 85% of human cancers and in only a limited number of somatictissues (Kim, N et al. (1994) Science 266: 2011-2013). Tumor antigen mayalso be “neo-antigens” expressed in cancer cells because of somaticmutations that alter protein sequence or create fusion proteins betweentwo unrelated sequences (i.e. bcr-abl in the Philadelphia chromosome).

Other tumor vaccines may include the proteins from viruses implicated inhuman cancers such a Human Papilloma Viruses (HPV), Hepatitis Viruses(HBV and HCV) and Kaposi's Herpes Sarcoma Virus (KHSV). Another form oftumor specific antigen which may be used in conjunction with PDL1blockade (such as PDL1 antibody, e.g., PDL1-binding molecule of theinvention) is purified heat shock proteins (HSP) isolated from the tumortissue itself. These heat shock proteins contain fragments of proteinsfrom the tumor cells and these HSPs are highly efficient at delivery toantigen presenting cells for eliciting tumor immunity (Suot, R &Srivastava, P (1995) Science 269:1585-1588; Tamura, Y. et al. (1997)Science 278:117-120).

Dendritic cells (DCs) are potent antigen presenting cells that can beused to prime antigen-specific responses. DCs can be produced ex vivoand loaded with various protein and peptide antigens as well as tumorcell extracts (Nestle, F. et al. (1998) Nature Medicine 4: 328-332). DCsmay also be transduced by genetic means to express these tumor antigensas well. DCs have also been fused directly to tumor cells for thepurposes of immunization (Kugler, A. et al. (2000) Nature Medicine6:332-336). As a method of vaccination, DC immunization may beeffectively combined with PDL1 blockade (such as PDL1 antibody, e.g.,PDL1-binding molecule of the invention) to activate more potentanti-tumor responses.

CAR-T (Chimeric Antigen Receptor T-Cell Immunotherapy) is another celltherapy for treating tumors. Chimeric Antigen Receptor T-Cell (CAR-Tcells) are T cells from a patient that have been genetically infectedwith a chimeric protein of an antigen-binding moiety of an antibodyagainst certain tumor antigen coupled with CD3-ζ chain or intracellularportion of FcεRIγ for expressing a chimeric antigen receptor (CAR).Also, co-stimulate signaling sequence may be introduced for increasingcytotoxic activity, proliferation and survival of T cells, and promotingthe release of cytokines. After reprogramming, T cells from the patientexpanded in vitro to produce a large number tumor-specific CAR-T cellswhich are then transfused back into the patient for treating tumor. PDL1blocking agents (such as PDL1 antibodies, e.g., the PDL1 bindingmolecule of the invention) may be used in combination with CAR-T celltherapy for activate stronger anti-tumor response.

PDL1-binding molecule of the invention may also be combined withstandard cancer treatments. PDL1-binding molecule of the invention maybe effectively combined with chemotherapeutic regimes. In theseinstances, it may be possible to reduce the dose of chemotherapeuticreagent administered (Mokyr, M. et al. (1998) Cancer Research 58:5301-5304). An example of such a combination is an anti-PDL1 antibody incombination with decarbazine for the treatment of melanoma. Anotherexample of such a combination is an anti-PDL1 antibody in combinationwith interleukin-2 (IL-2) for the treatment of melanoma. The scientificrationale behind the combined use of PDL1-binding molecule of theinvention and chemotherapy is that cell death, that is a consequence ofthe cytotoxic action of most chemotherapeutic compounds, should resultin increased levels of tumor antigen in the antigen presentationpathway. Other combination therapies that may result in synergy withPDL1 blockade through cell death are radiation, surgery, and hormonedeprivation. Each of these protocols creates a source of tumor antigenin the host. Angiogenesis inhibitors may also be combined withPDL1-binding molecule of the invention. Inhibition of angiogenesis leadsto tumor cell death which may feed tumor antigen into host antigenpresentation pathways.

The PDL1 binding molecule of the invention can also be used incombination with antibody against other tumor-specific antigen. Saidantibody against other tumor-specific antigen includes but not limitedto anti-EGFR antibody, anti-EGFR variant antibody, anti-VEGFa antibody,anti-HER2 antibody, or anti-CMET antibody. Preferably, said antibody isan monoclonal antibody.

PDL1-binding molecule of the invention can also be used in combinationwith bispecific antibodies that target Fc alpha or Fc gammareceptor-expressing effectors cells to tumor cells (see, e.g., U.S. Pat.Nos. 5,922,845 and 5,837,243). Bispecific antibodies can be used totarget two separate antigens. For example anti-Fc receptor/anti tumorantigen (e.g., Her-2/neu) bispecific antibodies have been used to targetmacrophages to sites of tumor. This targeting may more effectivelyactivate tumor specific responses. The T cell arm of these responseswould by augmented by the use of PDL1 blockade. Alternatively, antigenmay be delivered directly to DCs by the use of bispecific antibodieswhich bind to tumor antigen and a dendritic cell specific cell surfacemarker.

Tumors evade host immune surveillance by a large variety of mechanisms.Many of these mechanisms may be overcome by the inactivation of proteinswhich are expressed by the tumors and which are immunosuppressive. Theseinclude among others TGF-beta (Kehrl, J. et al. (1986) J. Exp. Med. 163:1037-1050), IL-10 (Howard, M. & O'Garra, A. (1992) Immunology Today 13:198-200), and Fas ligand (Hahne, M. et al. (1996) Science 274:1363-1365). Antibodies to each of these entities may be used incombination with PDL1-binding molecule of the invention to counteractthe effects of the immunosuppressive agent and favor tumor immuneresponses by the host.

Other antibodies which may be used to activate host immuneresponsiveness can be used in combination with anti-PDL1. These includemolecules on the surface of dendritic cells which activate DC functionand antigen presentation. Anti-CD40 antibodies are able to substituteeffectively for T cell helper activity (Ridge, J. et al (1998) Nature393: 474-478) and can be used in conjunction with PDL1-binding moleculeof the invention (Ito, N. et al (2000) Immunobiology 201 (5) 527-40).Activating antibodies to T cell costimulatory molecules such as OX-40(Weinberg, A. et al. (2000) Immunol 164: 2160-2169), 4-1BB (Melero, 1.et al. (1997) Nature Medicine 3: 682-685 (1997), and ICOS (Hutloff, A.et al (1999) Nature 397: 262-266) as well as antibodies which block theactivity of negative costimulatory molecules such as CTLA-4 (e.g., U.S.Pat. No. 5,811,097) or BTLA (Watanabe, N. et al. (2003) Nat Immunol4:670-9), B7-H4 (Sica, G L et al (2003) Immunity 18:849-61) may alsoprovide for increased levels of T cell activation.

Bone marrow transplantation is currently being used to treat a varietyof tumors of hematopoietic origin. While graft versus host disease is aconsequence of this treatment, therapeutic benefit may be obtained fromgraft vs. tumor responses. PDL1 blockade can be used to increase theeffectiveness of the donor engrafted tumor specific T cells. There arealso several experimental treatment protocols that involve ex vivoactivation and expansion of antigen specific T cells and adoptivetransfer of these cells into recipients in order to antigen-specific Tcells against tumor (Greenberg, R. & Riddell, S. (1999) Science 285:546-51). These methods may also be used to activate T cell responses toinfectious agents such as CMV. Ex vivo activation in the presence ofPDL1-binding molecule of the invention may be expected to increase thefrequency and activity of the adoptively transferred T cells.

Infectious Diseases

Other methods of the invention are used to treat patients that have beenexposed to particular toxins or pathogens. Accordingly, another aspectof the invention provides a method of preventing or treating aninfectious disease in a subject comprising administering to the subjecta PDL1-binding molecule of the invention, such that the subject istreated for the infectious disease.

Similar to its application to tumors as discussed above, PDL1 blockadecan be used alone, or as an adjuvant, in combination with vaccines, tostimulate the immune response to pathogens, toxins, and self-antigens.Examples of pathogens for which this therapeutic approach may beparticularly useful, include pathogens for which there is currently noeffective vaccine, or pathogens for which conventional vaccines are lessthan completely effective. These include, but are not limited to HTV,Hepatitis (A, B, & C), Influenza, Herpes, Giardia, Malaria. Leishmania,Staphylococcus aureus, Pseudomonas Aeruginosa. PDL1 blockade isparticularly useful against established infections by agents such as HIVthat present altered antigens over the course of the infections. Thesenovel epitopes are recognized as foreign at the time of anti-human PDL1administration, thus provoking a strong T cell response that is notdampened by negative signals through PDL1.

Some examples of pathogenic viruses causing infections treatable bymethods of the invention include HIV, hepatitis (A, B, or C), herpesvirus (e.g., VZV, HSV-1, HAV-6, HSV-II, and CMV, Epstein Barr virus),adenovirus, influenza virus, flaviviruses, echovirus, rhinovirus,coxsackie virus, cornovirus, respiratory syncytial virus, mumps virus,rotavirus, measles virus, rubella virus, parvovirus, vaccinia virus,HTLV virus, dengue virus, papillomavirus, molluscum virus, poliovirus,rabies virus, JC virus and arboviral encephalitis virus.

Some examples of pathogenic bacteria causing infections treatable bymethods of the invention include chlamydia, rickettsial bacteria,mycobacteria, staphylococci, streptococci, pneumonococci, meningococciand conococci, klebsiella, proteus, serratia, pseudomonas, legionella,diphtheria, salmonella, bacilli, cholera, tetanus, botulism, anthrax,plague, leptospirosis, and Lyme's disease bacteria.

Some examples of pathogenic fungi causing infections treatable bymethods of the invention include Candida (albicans, krusei, glabrata,tropicalis, etc.). Cryptococcus neoformans, Aspergillus (fumigatus,niger, etc.), Genus Mucorales (mucor, absidia, rhizophus), Sporothrixschenkii, Blastomyces dermatitidis, Paracoccidioides brasiliensis,Coccidioides immitis and Histoplasma capsulatum.

Some examples of pathogenic parasites causing infections treatable bymethods of the invention include Entamoeba histolylica, Balantidiumcoli, Naeglerialowleri, Acanthamoeba sp., Giardia lambia,Cryptosporidium sp., Pneumocystis carinii, Plasmodium vivax, Babesiamicroti, Trypanosoma brucei, Trypanosoma cruzi, Leishmania donovani,Toxoplasma gondi, Nippostrongylus brasiliensis.

In all of the above methods. PDL1 blockade can be combined with otherforms of immunotherapy such as cytokine treatment (e.g., interferons,GM-CSF, G-CSF, IL-2), or bispecific antibody therapy, which provides forenhanced presentation of tumor antigens (see, e.g., Holliger (1993)Proc. Natl. Acad. Sci USA 90:6444-6448; Poljak (1994) Structure2:1121-1123).

Autoimmune Reactions

Anti-PDL1 antibodies may provoke and amplify autoimmune responses.Therefore, it is possible to consider using anti-PDL1 blockade inconjunction with various self proteins in order to devise vaccinationprotocols to efficiently generate immune responses against these selfproteins for disease treatment.

For example, Alzheimer's disease involves inappropriate accumulation ofAβpeptide in amyloid deposits in the brain; antibody responses againstamyloid are able to clear these amyloid deposits (Schenk et al., (1999)Nature 400: 173-177). Other self proteins may also be used as targetssuch as IgE for the treatment of allergy and asthma, and TNFa forrheumatoid arthritis. Finally, antibody responses to various hormonesmay be induced by the use of anti-PDL1 antibody. Neutralizing antibodyresponses to reproductive hormones may be used for contraception.Neutralizing antibody response to hormones and other soluble factorsthat are required for the growth of particular tumors may also beconsidered as possible vaccination targets.

Analogous methods as described above for the use of anti-PDL1 antibodycan be used for induction of therapeutic autoimmune responses to treatpatients having an inappropriate accumulation of other self-antigens,such as amyloid deposits, including AP in Alzheimer's disease, cytokinessuch as TNFa, and IgE.

Chronic Inflammatory Diseases

Anti-PDL1 antibodies may also be used to treat diseases such as chronicinflammatory diseases, such as lichen planus, a T-cell mediated chronicinflammatory mucocutaneous disease (Youngnak-Piboonratanakit et al.(2004) Immunol Letters 94:215-22). Accordingly, in another aspect theinvention provides a method of abrogating chronic inflammatory diseaseby T cells, comprising administering to the subject a PDL1-bindingmolecule of the invention.

Vaccine Adjuvant

In one aspect, the invention provides use of PDL1-binding molecule ofthe invention as vaccine adjuvant. Anti-PDL1 antibodies may be used tostimulate antigen-specific immune responses by coadministration of ananti-PDL1 antibody with an antigen of interest (e.g., a vaccine).

Accordingly, in another aspect the invention provides a method ofenhancing an immune response to an antigen in a subject, comprisingadministering to the subject: (i) the antigen; and (ii) a PDL1-bindingmolecule of the invention, such that an immune response to the antigenin the subject is enhanced. The antigen can be, for example, a tumorantigen, a viral antigen, a bacterial antigen or an antigen from apathogen. Non-limiting examples of such antigens include those discussedin the sections above, such as the tumor antigens (or tumor vaccines)discussed above, or antigens from the viruses, bacteria or otherpathogens described above.

Kit

Also within the scope of the present invention are kits comprising thePDL1-binding molecule, immunoconjugate or pharmaceutical composition ofthe invention and instructions for use. The kit can further contain aleast one additional reagent, or one or more additional PDL1-bindingmolecules of the invention (e.g., binding molecules which bind todifferent epitopes in PDL1). Kits typically include a label indicatingthe intended use of the contents of the kit. The term label includes anywriting, or recorded material supplied on or with the kit, or whichotherwise accompanies the kit.

EXAMPLES

The present invention is further illustrated by the following examples,but the scope of the invention should not be limited to the specificexamples in any way.

Example 1: Screen of Heavy Chain Single Domain Antibody Against PDL1 1.1Library Construction

PDL1-Fc fusion protein (SEQ ID NO:28) for immunization was expressed byCHO cells (pCDNA4, Invitrogen, Cat V86220), purified by Protein Aaffinity chromatography. One Camelus bactrianus was chosen forimmunization. After 4 immunizations, lymphocytes were isolated from 100ml camel peripheral blood, and total RNA was extracted by RNA Extractionkit (QIAGEN). Extracted RNA was reverse transcribed into cDNA usingSuper-Script III FIRST STRANDSUPERMIX kit according to instructions.

Nucleic acid fragments encoding heavy chain antibodies were amplified bynested PCR:

First round PCR: Upstream primer: (SEQ ID NO: 29)GTCCTGGCTGCTCTTCTACAAGGC; Downstream primer: (SEQ ID NO: 30)GGTACGTGCTGTTGAACTGTTCC. Second round PCR:PCR products from first round PCR as template, Upstream primer:(SEQ ID NO: 31) GATGTGCAGCTGCAGGAGTCTGGRGGAGG; Downstream primer:(SEQ ID NO: 32) GGACTAGTGCGGCCGCTGGAGACGGTGACCTGGGT.

Target heavy chain single domain antibody nucleic fragments wererecovered and cloned into phage display vector pCDisplay-3 (CreativeBiolabs, Cat: VPT4023) using endonuclease PstI and NotI (from NEB). Theproducts were then electroporated into E. coli competent cell TG1, andphage display library for heavy chain single domain antibodies againstPDL1 was constructed and verified. By plating serial dilutions, librarycapacity was determined as 1.33×10⁸. To determine the insertion ratio ofthe library, 24 clones were randomly selected for colony PCR. Theresults revealed an insertion ratio of 100%.

1.2 Panning for Heavy Chain Single Domain Antibody Against PDL1

Multi-well plates were coated with PDL1-Fc fusion protein at 10 μg/well,4° C. overnight. On next day, after blocking with 1% skim milk at roomtemperature for 2 hours, 1001 μl phages (8×10¹¹ tfu, from the phagedisplay library for camel heavy chain single domain antibodiesconstructed in 1.1) were added, room temperature for 1 hour. Thenunbound phages were removed by washing with PBST (0.05% tween 20 in PBS)for 5 times. Phages that specifically bind to PDL1 were dissociated withtriethylammonium (100 mM), and used to infect E. coli TG1 of log phase,producing phages which were then purified for next round screen. Thesame screen was repeated for 3-4 rounds. Thereby, positive clones wereenriched, achieving the purpose of selecting PDL1 specific antibodiesfrom the antibody library by phage display technology.

1.3 Specific Selection of Individual Positive Clones by PhageEnzyme-Linked Immunoassay (ELISA)

PDL1 binding positive phages obtained after 3-4 rounds of panning wereused to infect blank E. coli and plated. 96 single colonies wererandomly selected for culturing, and phages were produced and purifiedrespectively. Plates were coated with PDL1-Fc fusion protein at 4° C.overnight; sample phages as obtained were added (blank phages ascontrol) and incubated at room temperature for 1 hour. Primary antibody,mouse anti-HA tag antibody (Beijing Kangwei Shiji Biotech. Ltd.), wasadded after washes and incubated at room temperature, 1 hour forreaction. Secondary antibody, goat anti-mouse alkaline phosphataselabeled antibody (Amyject Scientific Ltd.) was added after washes andincubated at room temperature, 1 hour for reaction. Alkaline phosphatasechromogenic solution was added after washes, and absorption value wasread at 405 nm wave length. When the OD of the sample well is 3 timeshigher than the OD of control well, the sample is determined aspositive. Bacteria in the positive wells were transferred to andcultured in LB liquid medium supplemented with 100 μg/ml Ampicillin forplasmid extraction and subsequent sequencing.

The protein sequences of each clone were analyzed according to thesequence alignment software Vector NTI. Clones with the same CDR1. CDR2,and CDR3 sequences are considered as the same antibody, while cloneswith different CDR sequences are considered as different antibody.

Example 2 Preliminary Evaluation of Heavy Chain Single Domain AntibodiesAgainst PDL1

2.1 Expression of Heavy Chain Single Domain Antibodies in E. coli andPurification Thereof

The coding sequence of the heavy chain single domain antibody obtainedby sequencing analysis was subcloned into the expression vector PET32b(Novagen, product number: 69016-3) and the correct recombinant plasmidwas transformed into expression host strain BL1 (DE3) (Tiangen Biotech,CB105-02), plated on LB solid medium containing 100 micrograms permilliliter ampicillin overnight at 37° C. Single colonies wereinoculated and cultured overnight, transferred in the next day forexpansion at 37° C. by shaking. When the culture reached OD value of0.6-1, 0.5 mM IPTG was added for induction, 28° C. overnight withshaking. The next day, the bacteria were harvested by centrifugation,and lysed to obtain antibody crude extracts. Nickel ion affinitychromatography was then used to purify the antibody proteins, resultingin antibody proteins of more than 90% purity.

2.2 Specific Binding of the Candidate PDL1 Heavy Chain Single DomainAntibody to Human PDL1 Protein

Plastes were coated with PDL1-Fc fusion protein overnight at 4° C. and100 ng of the heavy chain single-domain antibody obtained in Example 2.1(the control was a single domain antibody not binding to the PDL1-Fcprotein) was added to each well and allowed to react for 1 hour at roomtemperature. After washing, primary antibody anti-His tag antibody(purchased from Beijing Kangwei Century Biotechnology Co., Ltd.) wasadded and reacted for 1 hour at room temperature. After washing, asecondary goat anti-mouse horseradish peroxidase-labeled antibody(Yiqiao Shenzhou, Cat: SSA007200) was added and reacted for 1 hour atroom temperature. After washing, chromogenic agent was added and theabsorbance was read at 405 nm.

The plates were coated with Fc protein overnight at 4° C. and 100 ng ofthe heavy chain single domain antibody obtained in Example 2.1 was addedto each well (control was a single domain antibody against otherunrelated targets) and allowed to react for 1 hour at room temperature.After washing, an anti-rabbit anti-human Fc antibody (purchased fromShanghai Pu Xin Biotechnology Co., Ltd.) was added and reacted for 1hour at room temperature. After washing, goat anti-rabbit anti-rabbithorseradish peroxidase labeled antibody (purchased from Shanghai Pu XinBiotechnology Co., Ltd.) was added and reacted at room temperature for 1hour. After washing, chromogenic agent was added and the absorbance wasread at 405 nm.

The candidate antibody is considered as binding to the PDL1-Fc proteinwhen the ratio of the OD value for the PDL1-Fc protein divided by the ODvalue for the blank control is greater than or equal to 4; andsimultaneously, the above antibody capable of binding to PDL1-Fc antigenprotein, when the ratio of the OD value for binding to PDL1-Fc dividedby the OD value for binding Fc protein is >=5, is considered asspecifically binding to the PDL1 moiety rather than the Fc moiety.

The results showed that antibody No. 56 could specifically bind to PDL1without binding to Fc. The specific results are shown in the followingTable 1:

TABLE 1 OD OD SEQ (against (against OD OD ID PDL1) Fc) (PDL1/Fc)(PDL1/blank) NO PDL1-56 dAb 2.931 0.068 43.10294118 54.27777778 28 blank0.054 0.072 0.75 1

2.3 Binding of PDL1 Heavy Chain Single Domain Antibody to Mouse PDL1Protein

Mouse PDL1-Fc protein (SEQ ID NO: 33) was obtained by expression inHEK293 cells (pCDNA4, Invitrogen, Cat V86220).

The plates were coated overnight at 4° C. with mouse PDL1-Fc fusionprotein at 0.5 μg/well and 100 ng of the heavy chain single domainantibody obtained in Example 2.1 (control group is a single domainantibody against other unrelated target) was added and allowed to reactunder room temperature for 1 hour. After washing, primary antibodyanti-His tag antibody was added and reacted at room temperature for 1hour. After washing, goat anti-mouse horseradish peroxidase labeledantibody was added and reacted for 1 hour at room temperature. Afterwashing, chromogenic agent was added and the absorbance was read at 405nm. The results are shown in Table 2.

TABLE 2 OD (against mouse PDL1) PDL1-56 dAb 0.075 blank 0.096

It can be seen that the heavy chain single domain antibody of human PDL1of the present invention does not bind to the mouse PDL1-Fc protein.

2.4 Examination of the Blocking Effect of PDL1 Heavy Chain Single-DomainAntibody to the interaction of PD-1 and PDL1 by competitive ELISA

PDL1-Fc protein and PD1-Fc protein (SEQ ID NO: 34) were obtained byexpression in HEK293 cells (pCDNA4, Invitrogen, Cat V86220).Biotinylated protein PD1-Fc-Biotin was obtained using the ThermoBiotinlytion kit.

The plates were coated overnight at 4° C. with PDL1-Fc fusion protein at0.5 μg/well followed by addition of 100 ng of the heavy chain singledomain antibody obtained in Example 2.1 (controls are single domainantibodies against other unrelated targets or simply buffer) and 10 μgof PD1-Fc-Biotin (no antibody or protein was added to the blank group,only an equal volume of buffer was added), and allowed to react for 1hour at room temperature. SA-HRP (purchased from Sigma) was added andallowed to react for 1 hour at room temperature. After addingchromogenic solution, absorbance was read at 405 nm wavelength. When thesample OD value relative to the control OD value is <0.8, the antibodyis considered as possessing blocking effect.

As shown in Table 3, the antibody No. 56 showed a blocking effect on thePD-1/PDL1 interaction.

TABLE 3 OD Control 1 2.335 Control 2 2.413 blank 0.079 PDL1-56 0.129

2.5 the Blocking Effect of PDL1 Heavy Chain Single-Domain Antibody onPDL1 and PD-1 Interaction on Cell Surface was Investigated by FACS

HEK293 cells transiently expressing human PDL1 protein on the membrane(293-PDL1 cells) were obtained by transient transfection of a plasmidcarrying human PDL1 full length gene (pCDNA4, Invitrogen. Cat V86220)into human HEK293 cells.

293-PDL1 cells were harvested, resuspended in 0.5% PBS-BSA buffer in a96-well plate, and the above-mentioned antibodies to be detected wereadded. Negative controls were also set at the same time, and negativecontrols were 2 μg of a single domain antibody against other target. 0.3μg hPD-1-Fc-biotin and eBioscience SA-PE were added to all the samples,and the flow cytometry was performed after staining. The antibody isconsidered to block the cell-surface interaction of PDL1 and PD-1 if thefluorescence value is shifted to the blank direction as compared to theantibody-free group. In this way, antibodies that block the binding ofPDL1 antigen to PD-1 on the cell surface were identified.

The results are shown in FIG. 1, antibody No. 56 exhibits a blockingeffect on the PD-1/PDL1 interaction.

2.6 Binding Curves of PDL1 Heavy Chain Single Domain Antibodies to PDL1Antigen Protein

The plates were coated with the obtained PDL1 heavy chain single-domainantibody at 0.5 μg/well overnight at 4° C. followed by addition of agradient dilution series of PDL1-Fc fusion protein and allowed to reactfor 1 hour at room temperature. After washing, goat anti-human IgG-Fchorseradish peroxidase labeled antibody was added and allowed to reactfor 1 hour at room temperature. After washing, horseradish peroxidasecolor developing solution was added and the absorbance was read at awavelength of 405 nm. SotfMax Pro v5.4 was used for data processing andmapping analysis to get binding curve of the antibody to PDL1 and EC50value (about 5 ng/ml) through four-parameter fitting. The results areshown in FIG. 2.

2.7 Blocking Curves of PDL1 Heavy Chain Single-Domain Antibodies on theInteraction of PD-1 and PDL1

Plates were coated with PDL1-Fc fusion protein 0.5 μg/well overnight at4° C. followed by the addition of 100 uL of a gradient dilution series(containing 100 μg/mL PD1-Fc-Biotin) of 100 uL PDL1 blocking singledomain antibody Fc fusion protein per well, allowed to react for 1 hourat room temperature. SA-HRP (purchased from Sigma) was added and allowedto react for 1 hour at room temperature. After adding chromogenicsolution, absorbance was read at 405 nm wavelength.

SotfMax Pro v5.4 was used for data processing and mapping analysis toobtain blocking curve and IC50 value of antibody No. 56 to PDL1/PD-1through four-parameter fitting (IC50 for antibody No. 56 is 143 ng/mL).The results are shown in FIG. 3.

Example 3 Humanization of PDL1 Single Domain Antibodies

The humanization is performed by the method of protein surface aminoacid humanization (resurfacing) and universal framework grafting methodfor VHH humanization (CDR grafting to a universal framework).

The steps of humanization are as follows: The homologous modeling ofantibody No. 56 was performed with the modeling software Modeller9. Thereference homologous sequence is NbBcII10 antibody (PDB code: 3DWT), andthe relative solvent accessibility of the amino acids is calculatedaccording to the three-dimensional structure of the protein. If one ofthe amino acids of antibody No. 56 is exposed to a solvent, it wasreplaced with the amino acid at the same position of the reference humanantibody DP-47 sequence, until all substitutions were completed.

Specific steps of universal framework grafting method for VHHhumanization are as follows: First, universal humanized VHH frameworkh-NbBcII10FGLA (PDB code: 3EAK) designed by Cécile Vincke et al. basedon sequence homology, the framework was designed based on NanobodyNbBcII10 (PDB code: 3DWT); protein surface amino acid humanization wasperformed with reference to the human antibody DP-47, and partial aminoacids FGLA of VHH sequence framework 2 were modified. We directly usedh-NbBcII10FGLA as a framework and replaced the CDRs with the CDR regionsof antibody No. 56 to achieve humanization of the antibody.

The antibody No. 56 was humanized, and five humanized variants of theantibody No. 56 were obtained. Table 4 lists the SEQ ID No of thesehumanized variants as well as the amino acid changes therein, with aminoacid residue numbers following Kabat numbering. FIG. 4 shows thealignment of humanized sequences.

TABLE 4 K27F M28T S29F E44G R45L Q7IR N72D A74S S76N K83R P84A M89VHu56V1 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ (SEQ ID NO: 2) Hu56V2 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ (SEQID NO: 3) Hu56V3 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ (SEQ ID NO: 4) Hu56V4 ✓ ✓ ✓ ✓ ✓ ✓ ✓✓ ✓ ✓ ✓ ✓ ✓ (SEQ ID NO: 5) Hu56V5 ✓ ✓ ✓ ✓ ✓ ✓ ✓ (SEQ ID NO: 6)

Example 4 Preparation of PDL1 Blocking Antibody Protein Using MammalianCells 4.1 Preparation of Fc Fusion Protein of PDL1 Single DomainAntibody

The amino acid sequence of human IgG1-Fc region (SEQ ID NO: 7) wasobtained based on the constant region amino acid sequence of humanimmunoglobulin gamma1 (IgG1) from the protein database Uniprot (P01857).The nucleic acid fragment encoding human IgG1-Fc was obtained from humanPBMC total RNA by reverse transcription PCR, and the nucleic acidfragment encoding the fusion protein of PDL1 single domain antibodyobtained in the above Example and Fc was obtained by overlapping PCR,then subcloned into vector pCDNA4 (Invitrogen, Cat V86220). Fc regionsequences, such as SEQ ID NO: 8 or 9, in which ADCC activity or CDCactivity was removed by Site-directed mutagenesis, may also be used.

Recombinant single domain antibody-Fc fusion protein plasmid wastransfected into HEK293 cells for antibody expression. The recombinantexpression plasmids were diluted with Freestyle 293 medium and addedinto PEI (polyethylenimine) solution for transformation. Eachplasmid/PEI mixture was added to HEK293 cell suspension and incubated at37° C. and 10% CO₂ at 90 rpm. At the same time, 50 μg/L IGF-1 was added.Four hours later EX293 medium, 2 mM glutamine and 50 μg/L IGF-1 weresupplemented, cultured at 135 rpm. After 24 hours, 3.8 mM VPA was added.After cultured for 5 to 6 days, the transient expression supernatant wascollected and purified by Protein A affinity chromatography to obtainthe target PDL1 single domain antibody-Fc fusion protein.

The sequences of the PDL1 single domain antibody-Fc fusion proteins asobtained are shown in SEQ ID NOs: 10-27.

4.2 Preparation of PDL1 Antibodies from MedImmune LLC and Roche

The gene of anti-PDL1 antibody from MedImmune LLC. Inc. was cloned bythe method of 2.14H9 in US20130034559 and cloned into the vector pCDNA4.TM004 is Roche's anti-PDL1 antibody. The antibody gene was clonedaccording to YW243.55.S70.hIgG in US20130045201 A1, and cloned intovector pCDNA4.

The recombinant plasmid was transiently transfected into HEK293 cells bythe same method as in Example 4.1, and the resulting anti-PDL1 antibodyof MedImmune LLC was renamed as 2.41H90P; Roche's anti-PDL1 antibody wasrenamed as 243.55.

4.3 Comparison of the Expression of PDL1 Single-Domain Antibody FcFusion Protein and the Two Known PDL1 Antibodies

Using the same expression system and transient transfection conditions,the expression level of the Fc fusion protein of the PDL1 single domainantibody of the present invention was higher than 200 mg/L, while theexpression level of the antibody 2.41H90P was about 80 mg/L and theexpression level of the antibody 243.55 was about 40 mg/L. This resultindicates that the PDL1 single-domain antibody Fc fusion protein of thepresent invention is more stable in structure and can result in higherexpression level than the other two known PDL1 antibodies.

Example 5 Characterization of PDL1 Single Domain Antibody Fc FusionProtein 5.1 Binding Ability of PDL1 Single Domain Antibody Fc FusionProtein to PDL1 (by ELISA)

The PDL1-Chis protein (SEQ ID NO: 35) was obtained by transientexpression in HEK293 and purification with nickel column affinitychromatography. Plates were coated with the resulting PDL1-Chis proteinat 0.5 μg/well overnight at 4° C. Then gradient dilution series of PDL1single-domain antibody Fc fusion proteins obtained in the above Examplewere added and allowed to react for 1 hour at room temperature. Afterwashing, goat anti-human IgG-Fc horseradish peroxidase labeled antibodywas added and allowed to react for 1 hour at room temperature. Afterwashing, chromogenic agent was added and the absorbance was read at 405nm. SotfMax Pro v5.4 was used for data processing and mapping analysis,through the four-parameter fitting, to obtain binding curve and EC50value of the antibody to PDL1 (all test antibody EC50 value of about 150ng/mL) to reflect the affinity to PDL1.

The results are shown in FIG. 5, where the longitudinal coordinate isOD405 and the horizontal ordinate is the concentration of PDL1 singledomain antibody Fc-fusion protein (in ng/mL); inverted triangles,triangles, and squares represent the three different humanized forms ofFc fusion proteins: hu56v1-Fc, hu56v2-Fc, hu56v5-Fc. The three proteinshave comparable affinity for PDL1.

5.2 Identification of the Binding Ability of PDL1 Single-Domain AntibodyFc Fusion Protein to PDL1 (SPR Method) and Compared with KnownAntibodies

The binding kinetics of the PDL1 single domain antibody Fc fusionprotein to recombinant human PDL1 obtained in the above examples wasmeasured by the surface plasmon resonance (SRP) method using a BIAcoreX100 instrument. Recombinant human PDL1-Fc was coated directly onto aCM5 biosensor chip to obtain approximately 1000 response units (RU). Forkinetic measurements, the antibodies were serially diluted (1.37 to 1000nm) in HBS-EP+1× buffer (GE, cat # BR-1006-69) and injected for 120 s at25° C. with a dissociation time of 30 min, regenerated with 10 mMGlycine-HCl (pH 2.0) for 120 s. Binding rates (kon) and dissociationrates (koff) were calculated using a simple one-to-one Languir bindingmodel (BIAcore Evaluation Software version 3.2). The equilibriumdissociation constant (kD) is calculated as the ratio koff/kon.

The measured binding affinities of anti-PDL1 antibodies are shown inTable 5. The results show that the affinity of PDL1-56-Fc protein to thePDL1 target protein is significantly higher than that of two PDL1antibodies known in the art, and its higher Ka and lower Kd valuesindicate that the antibody fusion protein can bind PDL1 antigen morerapidly and thus is difficult to dissociate, which further shows thatPDL1-56-Fc as a blocking antibody, with properties better than the twoknown PDL1 antibody.

TABLE 5 Ka Kd KD PDL1-56-Fc 1.796E+6 1.432E−5 7.975E−12 PDL1-hu56V2-Fc2.123E+6 1.820E−5 8.573E−12 PDL1-56 3.323E+6 8.213E−4 2.472E−10 2.41H90P7.949E+5 6.160E−5 7.750E−11 243.55 4.481E+5 6.055E−5 1.351E−10

5.3 Blocking Effect of PDL1 Single Domain Fc Fusion Protein on PDL1-PD1Interaction (by Competitive ELISA)

Plates were coated with PDL1-Fc fusion protein 0.5 μg/well overnight at4° C., followed by addition of gradient dilution series (containing 100μg/mL PD1-Fc-Biotin) of the PDL1 single-domain antibody Fc fusionprotein obtained in the above Example at 100 μL per well, allowed toreact for 1 hour at room temperature. After washing, SA-HRP (purchasedfrom Sigma) was added and allowed to react at room temperature for 1hour. After washing, chromogenic agent was added and the absorbance wasread at 405 nm.

SotfMax Pro v5.4 was used for data processing and mapping analysis,through the four-parameter fitting, to obtain blocking curve and IC50value of the antibody to PDL1-PD1. The results are shown in FIG. 6,where longitudinal coordinate is OD405 and the abscissa is theconcentration of the PDL1 single domain antibody Fc fusion protein (inng/mL); the inverted triangle, the trigonometric triangle and the squarerepresent the three different humanized forms of Fc fusion proteins:hu56v1-Fc, hu56v2-Fc, hu56v5-Fc. The three proteins have similar abilityto block the PDL1-PD1 interaction.

5.4 Blocking Effect of PDL1 Single Domain Fc Fusion Protein on PDL1-CD80Interaction (by Competitive ELISA)

The CD80-Fc protein (SEQ ID NO: 36) was obtained from HEK293 cells.Biotinylated protein CD80-Fc-Biotin was obtained using the ThermoBiotinlytion kit.

Plates were coated with PDL1-Fc fusion protein 0.5 μg/well overnight at4° C., followed by addition of gradient dilution series (containing 300μg/mL CD80-Fc-Biotin) of the PDL1 single-domain antibody Fc fusionprotein obtained in the above Example at 100 μL per well, allowed toreact for 1 hour at room temperature. After washing, SA-HRP (purchasedfrom Sigma) was added and allowed to react at room temperature for 1hour. After washing, chromogenic agent was added and the absorbance wasread at 405 nm.

SotfMax Pro v5.4 was used for data processing and mapping analysis,through the four-parameter fitting, to obtain blocking curve and IC50value of the antibody to PDL1-CD80. The results are shown in FIG. 7,where the longitudinal coordinate is OD405 and the abscissa is theconcentration (in ng/mL) of PDL1 single domain antibody Fc fusionprotein hu56V2-Fc. The results show that PDL1 blocking single-domainantibody Fc fusion protein hu56V2-Fc can effectively block theinteraction between PDL1 and CD80.

5.5 Blocking Effect of PDL1 Single Domain Fc Fusion Protein on PDL1-PD1Interaction (by FACS)

Human HEK293 cells transiently express monkey PDL1 protein on membranesby transient transfection of plasmids containing the full length humanPDL1 gene.

PD1-muFc (SEQ ID NO: 39) at a working concentration of 2 μg/ml was addedto each group according to a 5×10⁵ cells/tube grouping, and thendifferent concentrations of KN035 were added to each group. Afterincubating on ice for 30 min and washing for three times, PE-labeledgoat-anti-mouse secondary antibody was added as the detection antibody,and the fluorescence intensity was detected by flow cytometry afterincubation on ice for 30 minutes.

GraphPad Prism software was used for data processing and mappinganalysis. By four-parameter fitting, the blocking curve and IC50 valueof the antibody on the direct interaction between PDL1 expressed on 293cell membrane and soluble PD1 were obtained. The results are shown inFIG. 8, wherein the longitudinal ordinate is MFI and the abscissa is theconcentration (in μg/mL) of the PDL1 single domain antibody fusionprotein hu56V1-Fcm1. The results show that PDL1 single-domain antibodyFc fusion protein could effectively block the interaction between PDL1expressed on 293 cell membrane and PD1.

Plasmid containing human PD1 full-length gene was transformed andintegrated into Jurket cell line to obtain Jurket cell line stablyexpressing human PD1 protein which was named Jurket-PD1.

After incubation of Jurkat-PD1 cells with biotinylated PDL1-muFc (SEQ IDNO: 38) protein (30 μg/ml) for 30 min on ice, a gradient dilution ofPDL1 single domain antibody Fc fusion protein hu56V1-Fcm1 were added,incubated for 1 h on ice, washed for three times with PBS, and then1:250 diluted Streptavidin PE was added, incubated on ice for 30 min andwashed three times with PBS. Fluorescence intensity was detected by flowcytometry.

Data processing and mapping analysis were performed using GraphPad Prismsoftware. The blocking curves and IC50 values of the antibodies on thedirect interaction between Jurkat-PD1 and soluble PDL1-muFc protein wereobtained by four-parameter fitting. The results are shown in FIG. 9,where the longitudinal ordinate is MFI and the abscissa is theconcentration (in μg/mL) of the PDL1 single domain antibody fusionprotein hu56V1-Fcm1. The results show that PDL1 blocking single-domainantibody Fc fusion protein could effectively block the interactionbetween Jurkat-PD1 and PDL1.

5.6 Binding Specificity of the PDL1 Single Domain Antibody Fc FusionProtein for PDL1 Protein

Human HEK293 cells transiently express human PDL1 protein on membranesby transient transfection of a plasmid carrying the full-length human B7family protein genes (pCDNA4, Invitrogen, Cat V86220). The plasmid alsoallows the C-terminus of the target protein to be fused to the EGFPprotein so that the level of B7 family protein expressed on the membranecan be examined by green fluorescence intensity. The constructedtransient transfected cell lines include 293-PDL1-EGFP, 293-PDL2-EGFP,293-B7H3-EGFP and 293-B7H3-EGFP.

The constructed cells were resuspended in 0.5% PBS-BSA buffer andhu56V2-Fc antibody was added. At the same time, a negative control of 2μg of a single domain antibody against other unrelated target was set upand incubated on ice for 20 minutes. After washing, eBiosciencesecondary antibody anti-hIg-PE was added, on ice for 20 min. Afterwashing, the cells were resuspended in 500 μl of 0.5% PBS-BSA buffer anddetected by flow cytometry.

The results are shown in FIG. 10. The upper row shows the control group,the lower row shows the sample groups. It is clear that hu56V2-Fcantibody specifically binds to human PDL1 protein only, not to other B7family proteins.

5.7 Binding of PDL1 Single Domain Antibody Fc Fusion Protein to MonkeyPDL1 Protein

Human HEK293 cells transiently express monkey PDL1 protein (SEQ ID NO:57) by transient transfection of plasmids containing the full length ofthe monkey PDL1 gene. The plasmid also allows the target proteinC-terminal fused to EGFP protein, which allows monkey PDL1 proteinmembrane expression levels can be investigated by green fluorescenceintensity.

The constructed cells were resuspended in 0.5% PBS-BSA buffer, hu56V2-Fcantibody was added and incubated on ice for 20 min. After washing,eBioscience secondary antibody anti-hIg-PE was added, on ice for 20 min.After washing, the cells were resuspended in 500 μl of 0.5% PBS-BSAbuffer and detected by flow cytometry.

The results are shown in FIG. 11. It is clear that the hu56V2-Fcantibody binds effectively to the monkey PDL1 protein.

5.8 PDL1 Single-Domain Antibody Fc Fusion Protein can EffectivelyIdentify PDL1 Positive Cell Population on the Patient's Tissue Sections

Tumor tissue sections of PDL1-positive lung cancer patients were stainedwith 5 μg/mL hu56V2-Fc antibody as primary antibody overnight andincubated with goat-anti-human HRP-labeled antibody (Perkin-Elmer. Cat:NEF802001EA), then visualized.

The results are shown in FIG. 12. hu56V2-Fc antibody can effectivelyidentify PDL1-positive cell population on lung cancer patient's tissuesections, and can simultaneously identify PDL1-positive tumor cells andPDL1-positive immune cells.

5.9 Activation of PBMC by PDL1 Single Domain Antibody Fc Fusion Protein

Peripheral blood mononuclear cells (PBMCs) were isolated from peripheralblood of healthy donors by density gradient centrifugation usingisolation solution for human lymphocytes (Tianjin Hao Yang).

2.5 μg/mL anti-CD3 antibody and gradient dilution series of PDL1 singledomain antibody Fc fusion protein hu56V2-Fc (also designated as KN035 inexperiment) were coated on cell culture plates overnight at 4° C. Thenext day, 1×10⁵ PBMCs were added to each well. After cultured for 5days, the supernatant was taken and the level of IFN-γ in thesupernatant was detected by IFN-γ ELISA kit (ebioscience).

The results are shown in FIG. 13. It can be seen that the PDL1single-domain antibody Fc fusion protein combined with anti-CD3 antibodycan enhance the secretion of γ-interferon from PBMC cells, ie, PDL1single domain Fc fusion protein enhances the activation of PBMC cells.At the same time, the activation effect is concentration-dependent.

5.10 Activation of CD4+ T Cells by PDL1 Single-Domain Antibody Fc FusionProtein in Dendritic Cell-T Cell Mixed Lymphoid Reaction and Comparisonwith Medimmune LLC Anti-PDL1 Antibody

Peripheral blood mononuclear cells (PBMCs) were isolated from whiteblood cells of peripheral blood from healthy donors by density gradientcentrifugation using isolation solution for human lymphocytes (TianjinHao Yang). They were then incubated with serum-free RPMI 1640 medium for1-2 hours to remove non-adherent cells and cells were cultured in RPMIcontaining 10% FBS, 10 ng/ml GM-CSF and 20 ng/mL IL-4. After culturingfor 5-6 days, 10 ng/ml of TNF-α was added and incubated for 24 hours toobtain mature dendritic cells.

Dendritic cells obtained by this method were resuspended in RPMIcomplete medium, 2×10⁵/ml. Then 50 ul per well was added to a 96-wellU-bottom plate (Costar: 3799) and cultured in an incubator.

CD4+ T cells were isolated from PBMC of another donor using a magneticbead isolation kit (Miltenyi Biotec: 130-096-533) following theinstructions of the manufacturer.

1×10⁴ dendritic cells and 1×10⁵ CD4+ T cells obtained by the abovemethods were mixed, resuspended in RPMI complete medium and added to a96-well culture plate, and 50 μl of the cell mixture was added to eachwell. 100 μl per well of hu56V2-Fc diluted in RPMI complete medium wasadded to a final antibody concentration of 0.1 μg/ml or 0 μg/ml.Supernatants were collected 5-7 days after culture, and IFN-γ level inthe supernatant was detected by IFN-γ ELISA kit (ebioscience).

The results are shown in FIG. 14A. It can be seen that PDL1single-domain antibody Fc fusion protein can enhance the IFN-γ secretionof CD4+ T cells in mixed lymphocyte reaction. That is, the PDL1 blockingsingle-domain antibody Fc fusion protein enhances T cell activation.

PBMCs from Subjects 1 were cultured with 50 ng/ml GM-CSF+25 ng/ml IL-4,and DCs were harvested 6 days after maturation with TNF-α (50 ng/ml);CD4+ T cells were sorted by magnetic bead isolation kit (MiltenyiBiotec: 130-096-533); DC cells were added to 96-well U-bottom plates at10⁴/well and 10⁵/well of CD4+ T cells were added after 2-4 h; differentconcentrations of PDL1 single domain antibody Fc fusion proteinhu56V1-Fcm1 or MedImmune LLC anti-PDL1 antibody 2.41H90P were added torespective wells; after culturing for 5 days, IFN-γ level in thesupernatant was detected by IFN-γ ELISA detection kit (ebioscience).

The results are shown in FIG. 14B, in which the gray histogram indicatesthat the stimulation of IFN-γ secretion by PDL1 single domain antibodyFc fusion protein and the black bar indicates MedImmune LLC anti-PDL1antibody 2.41H90P. PDL1 single-domain antibody Fc fusion protein withincreasing concentrations can enhance the ability of CD4+ T cells tosecrete IFN-γ in mixed lymphocyte reaction, and the ability of PDL1single domain antibody Fc fusion protein to activate T cells is slightlystronger than MedImmune LLC anti-PDL1 antibody 2.41H90P under the sameconcentration.

5.11 Stimulation of IL-2 Secretion of T Cells in Jurkat/Raji-PDL1 MixedCulture System by PDL1 Single-Domain Antibody Fc Fusion Protein andComparison with MedImmune LLC Anti-PDL1 Antibody

We constructed a T cell activation system, the Jurkat/Raji-PDL1co-culture system, to test the effect of PDL1 single domain antibody Fcfusion protein on T cell activation, which was compared with MedImmuneLLC anti-PDL1 antibody.

The system uses Jurkat cells (T cells) as effector cells and anti-humanCD3 antibody as the first signal for activation of Jurkat cells. B7family CD80 on the surface of Raji-PDL1 cells which are geneticallyengineered and stably expressing human PDL1, provides a secondco-stimulatory signal to activate Jurket cells, while PDL1 highlyexpressed on the same cell surface, acts as a negative regulator bybinding PD1 to inhibit Jurket cell activation.

Gradient dilutions of hu56V1-Fcm1 and 2.41H90P antibody proteins wereprepared using 10% FBS+1640+150 ng/ml anti-CD3; Jurkat and Raji-PDL1cells were adjusted to 3×10⁶ cells/ml and 1.5×10⁶ cells/ml, 50 ul wasadded to each well, stored at 37° C. for 24 hours. 100 ul of culturesupernatant was removed and measured for the expression of IL-2 withkit.

FIG. 15 shows the case where the black histogram indicates stimulationof IL-2 secretion by PDL1 single domain antibody Fc fusion protein andthe gray histogram indicates MedImmune LLC anti-PDL1 antibody 2.41H90P.PDL1 single-domain antibody Fc fusion protein can enhance the ability ofJurkat cells to secrete IL-2 with increasing concentration, and itsability to activate Jurkat cells is slightly stronger than that ofMedImmune LLC PDL1 antibody 2.41H90P at the same concentration.

5.12 Affinity of PDL1 Single-Domain Antibody Fc Fusion Protein to FcRn

Biotinylated PDL1 single domain antibody Fc fusion proteins hu56V1-Fc,hu56V2-Fc, hu56V1-Fcm1 and hu56V2-Fcm1 were diluted to 10 μg/ml andimmobilized onto SA biosensors. Human FcRn protein (RnD Systems Cat. No.8639-FC) was diluted 200 nM, 100 nM, 50 nM, 25 nM, 12.5 nM. Interactionwas detected using Octet K2 from Fortebio Corporation, with solidifyingfor 100 s curing binding for 60 s, dissociation for 30 s.

Table 6 shows that the average KD of PDL1 single-domain antibody Fcfusion proteins to FcRn is about 5.1E−07M. There was no significantdifference in affinity between mutant Fc (Fcm1) and wild-type Fc.

TABLE 6 KD (M) kon (1/Ms) kdis (1/s) hu56V1-Fc 5.13E−07 1.95E+051.00E−01 hu56V2-Fc 5.05E−07 2.10E+05 1.06E−01 hu56V1-Fcm1 5.10E−071.89E+05 9.63E−02 hu56V2-Fcm1 5.10E−07 2.34E+05 1.19E−015.13 CDC and ADCC Activity of PDL1 Single Domain Antibody Fc FusionProtein with Mutant Fc

PBMCs were activated with 300 IU/ml IL-2 for 24 hours as effector cells,with cell number of 8×10⁵ cells/well; Raji-PDL1 stably expressing humanPDL1 protein was used as target cells with a cell number of 2×10⁵cells/well; various concentration of hu56V1-Fcm1 or Rituxan protein aspositive control were added, and ADCC activity (%) under eachconcentration was measured using a CytoTox 96, non-radioactivecytotoxicity detection kit after incubation at 37° C. for 6 hours.

FIG. 16A shows that hu56V1-Fcm1 showed no significant ADCC activity ascompared to the positive control Rituxan.

Raji-PDL1 cells are used as target cells with a cell number of 2×10⁴cells/well and 5% of cynomolgus serum for providing complements,different concentrations of hu56V1-Fcm1 and positive control Rituxanwere added, cultured at 37° C. for 2 h. CDC activity of the sample wasdetected using CCK-8.

FIG. 16B shows that hu56V1-Fcm1 has no CDC activity at concentrationsranging from 0.02 μg/ml to 20 μg/ml compared to the positive control.

5.14 Inhibitory Activity of PDL1 Single Domain Antibody Fc FusionProtein on Tumor Growth

Immunodeficient NOD/SCID (non-obese diabetic/severe combinedimmunodeficiency) mice were used for studying in vivo activity of thePDL1 single domain antibody Fc fusion protein, hu56V2-Fc that cannotrecognize mouse PDL1. The purpose of this study was achieved byexperiments in which NOD/SCID mice were subcutaneously transplanted withhuman PDL1-expressing melanoma cell line A375 (ATCC, CRL-1619™) andhuman peripheral blood mononuclear cells (PBMCs). A375 and PBMC weremixed in a 5:1 ratio prior to injection and subcutaneously injected in atotal volume of 100 μl (containing 5 million A375 and 1 million PBMCs).Antibodies were administered intraperitoneally 24 hours after tumorinoculation and then once a week at a dose of 0.3 mg/kg; PBS served as anegative control. 4-6 mice per experimental group. Tumor formation wasobserved twice weekly and the long and short diameters of the tumorswere measured with a vernier caliper. The tumor volume was calculatedand the tumor growth curve was plotted (see FIG. 17A). It can be seenthat antibody hu56V2-Fc at 0.3 mg/kg dose significantly inhibited tumorgrowth.

The same in vivo model was used to examine the PDL1 single domainantibody Fc fusion protein, hu56V1-Fcm1, that did not recognize mousePDL1 either. A375 and human PBMCs were inoculated into NOD-SCID micesubcutaneously at a ratio of 4:1. Four hours later, different doses ofhu56V1-Fcm1 (0.1, 0.3, 1, 3 and 10 mg/kg) were administeredintraperitoneally. Anti-tumor effect to A375/human PBMCs xenografts inNOD-SCID mice was studied after weekly administration for 4 weeks. PBSwas used as a negative control. 4-6 mice per experimental group. Tumorformation was observed twice weekly and the major and minor diameters ofthe tumors were measured using a vernier caliper. The tumor volume wascalculated and the tumor growth curve was plotted (see FIG. 17B). Theresults show that all doses of hu56V1-Fcm1 (0.1-10 mg/kg) hadsignificant anti-tumor effect on A375/human PBMCs allogeneic xenograftsof NOD-SCID mice, but without significant dose-relevance. Antibodyhu56V1-Fcm1 significantly inhibited tumor growth even at a dose of 0.1mg/kg.

5.15 Inhibitory Activity on Tumor Growth of PDL1 Single-Domain AntibodyFc Fusion Protein Administered for Different Times

NOD-SCID mouse A375/human PBMCs xenograft tumor model was used. A375with human PBMCs at a ratio of 4:1 was subcutaneously inoculated toNOD-SCID mice and hu56V1-Fcm1 (0.3 mg/kg) was injected intraperitoneally4 hours later followed by intraperitoneal administration once everythree days. The final numbers of administration were 1, 2, 3, 4 times.Tumor formation was observed every three days and the major and minordiameters of the tumors were measured with a vernier caliper tocalculate the tumor volume until the 33rd day from the firstadministration. The tumor growth curve was plotted (FIG. 18). Theresults showed that different number of administration in the studyperiod all had significant antitumor effects on A375/human PBMCsallogeneic xenografts of NOD-SCID mice.

5.16 Inhibition of Tumor Growth by PDL1 Single Domain Antibody Fc FusionProtein and Comparison with MedImmune LLC Anti-PDL1 Antibody

The purpose of this study was achieved by experiments in which NOD/SCIDmice were subcutaneously transplanted with human PDL1-expressingmelanoma cell line A375 (ATCC, CRL-1619™) and human peripheral bloodmononuclear cells (PBMCs). A375 and PBMC were mixed in a 5:1 ratio priorto injection in a total volume of 100 μl (containing 5 million A375 and1 million PBMCs). The antibodies were administered intraperitoneally for24 hours after tumor inoculation and then weekly once, at a dose of 1mg/kg. The treatment group included hu56V2-Fc (denoted hu56) andMedImmune LLC's anti-PDL1 antibody group (indicated as 2.41) with PBS asa negative control. 4-6 mice per experimental group. Tumor formation wasobserved twice a week, and the major and minor diameters of the tumorswere measured with a vernier caliper. The tumor volume was calculatedand the tumor growth curve was plotted (see FIG. 19 A). MedImmune LLC'santi-PDL1 antibody was essentially ineffective in this model and thetumor volume exceeded the negative control group on day 35, thus theadministration and tumor volume measurement were stopped. It can be seenthat the effect of hu56V2-Fc in inhibiting A375 tumor growth at 1 mg/kgdose is significantly superior to MedImmune LLC's anti-PDL1 antibody2.41H90P under this model.

Since anti-PDL1 antibodies from MedImmune LLC did not show tumorsuppression under the above system, it is possible that the activationof PBMC in the system is insufficient to inhibit tumor cell growth. Thusthe content of PBMC in mixed cells was increased for examining again theanti-tumor effect of MedImmune LLC anti-PDL1 antibody.

The A375 and PBMC were mixed 1:1 prior to injection in a total volume of100 μl (containing 5 million A375 and 5 million PBMCs) subcutaneouslyand MedImmune LLC anti-PDL1 antibody (2.41H90P) was administeredintraperitoneally followed by weekly administration at a dose of 1mg/kg; PBS was used as a negative control. 4-6 mice per experimentalgroup. Tumor formation was observed twice weekly and the major and minordiameters of the tumors were measured using a vernier caliper. The tumorvolume was calculated and the tumor growth curve was plotted (see FIG.19B). It can be seen that anti-PDL1 antibody from MedImmune LLC showsanti-tumor effect in in vivo model after increasing the proportion ofPMBC.

The mean tumor inhibition (TGI=(1−tumor volume of treatment group/tumorvolume of control group)×100%) on day 42 of the antibody is calculatedand presented in Table 7 below.

TABLE 7 TGI hu56V2-Fc 2.41H90P 5:1 65.7% N.A. 5:5 — 41.7%

The above in vivo antitumor experiment results show that the PDL1blocking single-domain antibody Fc fusion proteins of the presentinvention have significantly superiority to the known PDL1 blockingantibodies (Anti-PDL1 antibody from MedImmune LLC) in an in vivomelanoma A375 nude mouse model.

Example 6 Stability of PDL1 Single Domain Antibody Fc Fusion Protein 6.1Resistance of PDL1 Single Domain Antibody Fc Fusion Protein to Alkaliand Oxidative Stress

500 mM ammonium bicarbonate was used as alkali disrupting agent andfusion proteins were treated at 37° C. for 38 hours. 1% hydrogenperoxide was used as the oxidant, 8 hours treatment at room temperature

The changes in the biological activity of the PDL1 single-domainantibody Fc fusion protein obtained by the above Examples before andafter treatment were measured using competitive ELISA. As can be seen inFIG. 20, alkali and oxidative treatments did not affect the activity ofthe candidate PDL1 single domain antibody Fc fusion protein, and thecompetitive ELISA activity after 38 hours of alkali treatment was 103%relative to 0 hour. The competitive ELISA activity at 8 hours ofoxidation treatment was 106% relative to 0 hour.

6.2 Stability of PDL1 Single Domain Antibody Fc Fusion Protein at HighConcentration

The PDL1 single domain antibody Fc fusion protein was concentrated byUF/DF and exchanged into PBS buffer. And the aggregate formationtendency thereof was examined by SE-HPLC.

When concentrated to 200 mg/mL, the purity of the PDL1 single domain Fcfusion protein was 96.8% by SE-HPLC detection. Aggregates was increasedby about 2.4% over that at low concentrations (˜2 mg/mL). Throughout theconcentration process, no turbid phenomenon or aggregation occurred inthe protein solution.

Sequence listing >SEQ ID NO: 1 antibody Nb.56QVQLQESGGGLVQPGGSLRLSCAASGKMSSRRCMAWFRQAPGKERERVAKLLTTSGSTYLADSVKGRFTISQNNAKSTVYLQMNSLKPEDTAMYYCAADSFEDPTCTINTSSGAFQYWGQGTQVTVSS >SEQ ID NO: 2 Hu56V1QVQLVESGGGLVQPGGSLPLSCAASGKMSSRPCMAWFRQAPGKERERVAKLLTTSGSTYLADSVKGPFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSS >SEQ ID NO: 3 Hu56V2QVQLVESGGGIVQPGGSLRLSCPASGFTFSPRCMAWFRQAPGKEPERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSS >SEQ ID NO: 4 Hu56V3QVQLVESGGGLVQPGGSLRLSCAASGKMSSRRCMAWFRQAPGKGLERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLRAEDTAVYYGADSFEDPTCTLVTSSGAFQYWGQGTLVTVSS >SEQ ID NO: 5 Hu56V4QVQLVESGGGLVQPGGSLRLSCAASGFTFSRRCMAWFRQAPGKGLERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVS >SEQ ID NO: 6 Hu56V5QVQLVESGGGLVQPGGSLRLSCAASGKMSSRPCMAWFRQAPGKEPERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLKAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSS >SEQ ID NO: 7 IgG1-FcEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDINVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 8 IgG1-Fc-m1EPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVAVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAGIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDINVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 9 IgG1-Fc-m2EPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDINVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 10 56-FcQVQLQESGGGLVQPGGSLRLSCAASGKMSSRPCMAWFRQAPGKERERVAKILTTSGSTYLADSVKGRFTISQNNAKSTVYLOMNSLKTEDTAMYYQVADSFEDPTCTLVTSSGAFOYWGQGTQVTVSSEPKSCDKTHTOPPCPAPELLGGPSVFLEPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQBYTLPPSRDELTKNQVSLTCLVKGFYPSDIANEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMEEALHNHYTQKSLSLSPGK >SEQ ID NO: 11 Hu56V1-FcQVQLVESGGGLVQPGGSLPLSCAASGKMSSRPCMAWFRQAPGKERERVAKLLTTSGSTYLADSVKGPFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSCDKTHTCPPCPAPELIGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVENAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQTSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKITVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 12 Hu56V2-FcQVQLVESGGGLVQPGGSLRLSCAASGFTFSRRCMAWFRQAPGKEPERVAKLLTTSGSTYLADSVKGPFTISRDNSKNTVYLQMNSLRAEDTAVYYCPADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSCLKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVENAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 13 Hu56V3-FcQVQLVESGGGLVQPGGSLRLSCAASGKMSSRRCMAWFRQAPGKGLERVAKLLTTSGSTYLADSVYGRFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSPWQQGNVFSCSVMHEALHNHYTQKGLSLSPGK >SEQ ID NO: 14 Hu56V4-FcQVQLVESGGGLVQPGGSLRLSCAASGFTFSRRCMAWFRQAPGKGLERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTGLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 15 Hu56V5-FcQVQLVESGGGLVQPGGSLPLSCAASGKMSSRRCMAWFRQAPGKERERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLKAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVENAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 16 56-Fc-m1QVQLQESGGGLVQPGGSLRLSCAASGKMSSRRCMAWFRQAPGKERERVAKLLTTSGSTYLADSVKGRFTISQNNAKSTVYLQMNSLKPEDTAMYYCAADSFEDPTCTLVTSSGAFQYWGQGTQVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVAVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAGIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTGLVKGFYPSDIANEWESNGQPENNYKTTPPVLDSDGSFELYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 17 Hu56V1-Fc-m1QVQLVESGGGLVQPGGSLRLSCAASGKMSSRRCMAWFRQAPGKEPERVAKLLTTSGSTYLADSVKGPFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVAVSHEDPEVKFNWYVDGVEVENAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAGIEKTISKAKGQPREPQVYTLPPSRDELTKNQTSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 18 Hu56V2-Fc-m1QVQLVESGGGLVQPGGSLRLSCAASGFTESRRCMAWFRQAPGKERERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVAVSHEDPEVKFNWYVDGVEVHNAKTKPREEWYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAGIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 19 Hu56V3-Fc-m1QVQLVESGGGLVOPGGSLRLSCAASGKMSSRRCMAWFRQAPGKGLERVAKILITSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLEPPKPKDTLMISRTPEVTCVVVAVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAGIEKTISKAKGQPREPOVYTLPPSRDELTKNOVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFELYSKLTVDKSPWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK > SEQ ID NO: 20 Hu56V4-Fc-m1QVQLVESGGGLVQPGGSLRLSCAASGFTFSRRCMAWFPRQAPGKGLERVAKLLTSGSTYLADSVKGRFTISRDNSKNMVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVAVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAGIEKTISKAKGQPREPQVYTLPPSPDELTKNQVSLTQLVKGFYPSDIANEWESNGQPENNYKTTPPVLDSDGSFELYSKLTVDKSRWQOGNVESCSVMHEALHNHYTQKSLSLSPGK > SEQ ID NO: 21 Hu56V5-Fc-m1QVQLVESGGGLVQPGGSLRLSCAASGKMSSRPCMAWFRQAPGKEPERVAKLLTTSGSTYLADSVKGPFTISRDNSKNTVTLQMNSLKAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVAVSHEDPEVKFNWYVDGVEVENAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAGIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVESCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO:22 56-Fc-m2QVQLQESGGGLVQPGGSLRLSCAASGKMSSRRCMAWFRQAPGKERERVAKLLTTSGSTYLADSVKGRFTISQNNAKSTVYLQMNSLKPEDTAMYYCAADSFEDPTCTLVTSSGAFQYWGQGTQVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFELYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO:23 Hu56V1-Fc-m2QVQLVESGGGLVQPGGSLRLSCPASGKMSSRRCMAWFRQAPGKEPERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTQLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 24 Hu56V2-Fc-m2QVQLVESGGGLVQPGGSLRLSCAASGFTFSRRCMAWFRQAPGKERERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSSDKTHTCPPCPAPELLGGPSVELFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVENAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKCKVSNKALTAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQTSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSPRQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 25 Hu56V3-Fc-m2QVQLVESGGGLVQPGGSLRLSCAASGKMSSRRCMAWFRQAPGKGLERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVEHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSPDELTKNQNSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKELSLSPGK >SEQ ID NO: 26 Hu56V4-Fc-m2QVQLVESGGGLVQPGGSLRLSCAASGFTFSRRCMAWFRQAPGKGLERVAKLLTTSGSTYLADSVKGRFTISRDNSKNTVYLQMNSLRAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 27 Hu56V5-Fc-w2QVQLVESGGGLVQPGGSLRLSCAASGKMSSRRCMAWFRQAPGKERERVAKLLTTSGSTYLADSVYGRFTISRDNSKNTVYLQMNSLKAEDTAVYYCAADSFEDPTCTLVTSSGAFQYWGQGTLVTVSSEPKSSDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYASTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVENESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 28 Human PDL1-FcTVTVPKDLYVVEYGSNMTIECKFPVEKQLDLAALIVYWEMEDKNIIQFVHGEEDLKVQHSSYRQRARLLKDQLSLGNAALQITDVKLQDAGVYRCMISYGGADYKRITVKVNAPYNKINQRILVVDPVTSEHELTCQAEGYPKAEVIWTSSDHQVLSGKTTTTNSKREENLFNVTSTLRINTTTNEIFYCTFRRLDPEENHTAELVIPELPLAHPPNERTDDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 29GTCCTGGCTGCTCTTCTACAAGGC >SEQ ID NO: 30GGTACGTGCTGTTGAACTGTTCC >SEQ ID NO: 31GATGTGCAGCTGCAGGAGTCTGGRGGAGG >SEQ ID NO: 32GGACTAGTGCGGCCGCTGGAGACGGTGACCTGGGT >SEQ ID NO: 33 mice PDL1-FcFTITAPKDLYVVEYGSNVTMECRFPVERELDLLALVVYWEKEDEQVIQFVAGEEDLKPQHSNFRGRASLPKDQLLKGNAALQITDVKLQDAGVYCCIISYGGADYKRITLKVNAPYRKINQRISVDPATSEHELICQAEGYPEAEVIWTNSDHQPVSGKRSVTTSRTEGMLLNVTSSLRVNATANDVFYCTFWRSQPGQNHTAELIIPELPATHPPQNRTHDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 34 Human PD1-FcPGWFLDSPDRPWNPPTFSPALLVVTEGDNATFTCSFSNTSESFVLNWYRMSPSNQTDKLAAFPEDRSQPGQDCRFPVTQLPNGRDFHMSVVRARRNDSGTYLCGAISLAPKAQIKESLRAELRVTERRAEVPTAHPSPSPRPAGQFQDKTHTCPPCRAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGOPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 35 PDL1-ChisTVTVPKDLYVVEYGSNMTIECKFPVEKQLDLAALIVYWEMEDKNIIQFVHGEEDLKVQHSSYRQRARLLKDQLSLGNAALQITDVKIQDAGVYRCMISYGGADYKRITVKVNAPYNKINQRILVVDPVTSEHELTCQAEGYPKAEVIWTSSDHQVLSGKTTTTNSKREENLFNVTSTLRINTTTNEIFYCTFRRLDPEENHTAELVIPELPLAHPPNERTDGSHHHHHHHH >SEQ ID NO: 36 CD80-FcVIHVTKEVKEVATLSCGHNVSVEELAQTRIYWQKEKKMVLTMMSGDMNIWPEYKNRTIFDITNNLSIVILALRPSDEGTYECVVLKYEKDAFKREHLAEVTLSVKADFPTPSISDFEIPTSNIRRIICSTSGGFPEPHLSWLENGEELNAINTTVSQDPETELYAVSSKLDFNMTTNHSFMCLIKYGHLRVNQTFNWNTTKQEHFPDNDKTHTCPPCPAPELLGGPSVFLFPPKTKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK >SEQ ID NO: 37 monkey PDL1FTVTVPKDLYVVEYGSNMTIECKFPVEKQLDLTSLIVYWEMEDKNIIQFVHGEEDLKVQHSNYRQRAQLLKDQLSLGNAALRITDVKLQDAGVYRCMISYGGADYKRITVKVNAPYNKINQRILVVDPVTSEHELTCQAEGYPKAEVIWTSSDHQVLSGKTTTTNSKREEKLLNVTSTLRINTTANEIFYCIFRRLDPEENHTAELVIPELPLALPPNERTHLVILGAIFLLLGVALTFIFYLRKGRKMDMKKSGIRVTNSKKQRDTQLEET >SEO ID NO: 38 human PDL1A-muFcFTVTVPKDLYVVEYGSNMTIECKFPVEKQLDLAALIVYWEMEDKNIIQFVHGEEDLKVQHSSYRQRARLLKDQLSLGNAALQITDVKLQDAGVYRCMISYGGADYKRITVKVNAPYNKINQRILVVDPVTSEHELTCQAEGYPKAEVIWTSSDHQVLSGKTTTTNSKREEKLFNVTSTLRINTTTNEIFYCTFRRLDPEENHTAELVIPELPLAHPPNERTDIEGRMDPKSSDKTHTCPPCPAPEVSSVFIFTPKPKDVLTITLTPKVTCVVVDISKDDPEVQFSWFVDDVEVHTAQTQPREEQFNSTFRSVSELPIMHQDWLNGKEFKCRVNSAAFPAPIEKTISKTKGRPKAPQVYTIPPPKEQMAKDKVSLTCMITDFFPEDITVEWQWNGQPAENYNNTQPIMNTNGSYFVYSKLNVQKSNWEAGNTFTCSVLHEGLHNHHTEKSLSHSPGK >SEO ID NO: 39 Human PD1-muFcPGWFLDSPDRPWNPPTFSPALLVVTEGDNATFTCSFSNTSESFVLNWYRMSPSNQTDKLAAFPEDRSQPGQDCRFPVTQLPNGRDFHMSVVRARRNDSGTYLCGAISLAPKAQIKESLRAELRVTERRAEVPTAHPSPSPRPAGQFQIEGRMDPKSSDKTHTCPPCPAPEVSSVFIFPPKPKDVLTITLTPKVTCVVVDISKDDPEVQFSWFVDDVEVHTAQTQPREEQFNSTFRSVSELPIMHQDWLNGKEFKCRVNSAAFPAPIEKTISKTKGRPKAPQVYTIPPPKEQMAKDKVSLTCMITDFFPEDITVEWQWNGQPAENYKNTQPIMNINGSYFVYSKLNVQKSNWEAGNTFTCSVLHEGEHNHHTEKSLSHSPGK

1. A programmed death ligand 1 (PDL1)-binding molecule, which canspecifically bind to PDL1 and consists of an amino acid sequence asshown in formula A-L-B, wherein A represents an immunoglobulin singlevariable domain, L is absent or represents an amino acid linker, and Brepresents a human immunoglobulin Fc region, wherein the immunoglobulinsingle variable domain consisting of an amino acid sequence selectedfrom SEQ ID NOs:1-6, said PDL1-binding molecule is capable of forminghomodimers via said human immunoglobulin Fc region.
 2. The PDL1-bindingmolecule of claim 1, wherein said immunoglobulin Fc region is a Fcregion of human IgG1, IgG2, IgG3 or IgG4.
 3. The PDL1-binding moleculeof claim 1, wherein said immunoglobulin Fc region is mutated to removeADCC and CDC activities.
 4. The PDL1-binding molecule of claim 1,wherein the sequence of said immunoglobulin Fc region is selected fromSEQ ID NOs:7-9.
 5. The PDL1-binding molecule of claim 1, wherein thelinker is 1-20 amino acids in length.
 6. The PDL1-binding molecule ofclaim 1, which consists of an amino acid sequence selected from SEQ IDNOs:10-27.
 7. The PDL1-binding molecule of claim 1, which has at leastone of the following features: (a) binding to human PDL1 with a KD ofless than 1×10⁻⁷ M; (b) blocking the interaction between PDL1 and PD-1;(c) enhancing activation of PBMCs and/or T cells; (d) inhibiting tumorgrowth.
 8. The PDL1-binding molecule of claim 1, which binds to PDL1with a KD of less than 1×10⁻⁷ M.
 9. A nucleic acid molecule encoding thePDL1-binding molecule of claim
 1. 10. An expression vector, whichcomprises the nucleic acid molecule of claim 9 operably linked to anexpression regulation element.
 11. A host cell, which comprises thenucleic acid molecule of claim 9 or is transformed with the expressionvector of claim 10, and is capable of expressing said PDL1-bindingmolecule.
 12. A method for producing the PDL1-binding molecule of claim1, which comprises: a) culturing the host cell of claim 11 underconditions that allow expression of the PDL1-binding molecule; b)recovering the PDL1-binding molecule expressed by the host cell from theculture of step a); and c) optionally further purifying and/or modifyingthe PDL1-binding molecule obtained from step b).
 13. A pharmaceuticalcomposition comprising the PDL1-binding molecule of claim 1, and apharmaceutically acceptable carrier.
 14. A method for preventing and/ortreating cancer in a subject, comprising administering an effectiveamount of the PDL11-binding molecule of claim 1 or the pharmaceuticalcomposition of claim 13 to the subject.
 15. The method of claim 14,further comprising administering additional anti-tumor therapeutic meansto said subject.
 16. The method of claim 15, wherein said additionalanti-tumor therapeutic means comprises chemotherapy, radiotherapy orantibody against other tumor-specific antigen.
 17. The method of claim16, wherein said antibody against other tumor-specific antigen comprisesanti-EGFR antibody, anti-EGFR variant antibody, anti-VEGFa antibody,anti-HER2 antibody, or anti-CMET antibody.
 18. The method of claim 17,wherein said antibody against other tumor-specific antigen is amonoclonal antibody.
 19. The method of claim 14, wherein said cancer isselected from the group consisting of lung cancer, ovarian cancer, coloncancer, rectal cancer, melanoma, renal cancer, bladder cancer, breastcancer, liver cancer, lymphoma, hematological malignancy, head and neckcancer, glioma, gastric cancer, nasopharyngeal cancer, laryngeal cancer,cervical cancer, corpus carcinoma, and osteosarcoma.
 20. A method forpreventing and/or treating infectious disease in a subject, comprisingadministering an effective amount of the PDL1-binding molecule of claim1 or the pharmaceutical composition of claim 13 to the subject.
 21. Themethod of claim 20, wherein said infectious disease is caused by apathogen selected from the group consisting of HIV, hepatitis virus,influenza virus, herpes virus, Giardia, plasmodium, Leishmania,Staphylococcus aureus, Pseudomonas aeruginosa.
 22. A method forpreventing and/or treating chronic inflammatory disease in a subject,comprising administering an effective amount of the PDL1-bindingmolecule of claim 1 or the pharmaceutical composition of claim 13 to thesubject.
 23. The method of claim 22, wherein said chronic inflammatorydisease is lichen planus or T-cell mediated chronic inflammatorymucocutaneous disease.
 24. (canceled)